First of all, I'd like to say say thanks to those on this small and friendly part of Flyertalk who helped me with planning my recent trip to Malaysia. I said I'd post a quick review, so here it is. I'll try and include some of the things which I found difficult to find when I was looking things up, so it'll hopefully help others.

I'm a pretty seasoned traveler, long and short haul and tend to fly J when I can although sometimes other cabins. I'm BAEC bronze right now, having dropped from gold via silver. Don't travel as much with work as I used to. I've flown BA a lot (all classes) although try not to if I can, QR a fair bit (all classes), QF (Y & J), CX (J), AA (Y & J) and a few others but I usually fly OW. Just for reference.

I flew with my wife and 2-year old.

This was my first time on MH - J out from LHR to Langkawi (really, really great place but this post is about the flights) and back in F, with the shorthaul in J.

Planning

Booking the flights was easy enough - a good deal on Expedia which has been talked about a lot on FT. MH's IT is not great though; as I hadn't booked direct I could do very little on the web site. I phoned up though and had seats allocated for me. I also made use of Chef on Call, which worked for my wife and I on the web site, but not my daughter. An email fixed that, but then I was told about COC being suspended from LHR. Not a big deal as I was planning to sleep as soon as I got on the plane.

At LHR

Check-in was easy. I did it online but we had bags to check in so used the counters at T4. No queue and couldn't be easier. The counters are nice and close to Fast Track which was empty, unlike every other time I'd been there.
We used the QR lounge - it really is a great lounge and the best one I've ever used. My daughter was a pain (over-excited) and a staff member asked me to control her (as I was trying to control here). Absolutely the right thing to do - kids react well to someone of authority telling them off so this was very welcome. It's something to bear in mind if you have kids and you're not keen on controlling them; it's a small lounge.

I didn't try the MH lounge, but didn't feel the need.

Getting onto the plane was easy enough; the gate was opposite the lounge although we'd already left after we finished eating to give others some peace.

Business Class on the A380

First of all, the seats do lie flat. Or almost flat; the two ends of the seat are higher than the middle, so it works fine when you're on your back or side, but isn't so great on your front. It's also quite short; I'm 6 foot tall and just about fit in. Tall people beware. People do criticise BA's CW seat, but it's perfectly flat and while narrow, is long enough for me at least. In general there is a good amount of space, especially in seat mode. Better than BA, better than QR (apart from their 777 which is pretty much exactly the same).
I had satay but skipped the rest of the food. Satay was good.
What did annoy me, and annoys me in general on overnight flights is the food service. Why is there a need to turn all the lights up full as soon as the seat belt sign goes off? People who want to eat can eat with their lamps and on an overnight flight, why can't people be encouraged to eat in the lounge beforehand? Surely flying east it makes sense to get your head down ASAP. At least it was a long flight but it did wake up my daughter and made her irritable which affected everyone.

Anyway, we all got a decent sleep in the end. Breakfast was OK (including the fruit) and we were in KUL on time.

KUL and the J lounges

If you're transferring international to domestic at KUL you will need to take the train from the satellite to the main terminal and go through passport control there. Double back at the train station and go downstairs - don't head to arrivals. The domestic lounge isn't as good as the one in the satellite, so if you have a lengthy transfer, use the satellite lounge, which we did.
The lounge itself isn't great. It's big and spacious but the food offering isn't fantastic, although it's edible. The showers, as another poster said last week, are pretty grotty. You have to submit your boarding pass to get a towel and soap and the showers themselves leak out of the door (I had to jump out and rescue my shoes before they got soaked). Really wasn't impressed.
The kids room in the lounge is also pretty terrible, with very few toys which were in a poor state.
I'd say the J lounge is one of the worst home airport lounges I've been to. Not as bad as AA lounges and way better than e.g. BA's GVA lounge (shudder). Comparing with the T5 lounges at LHR I'd say between GC South and the B gates lounge.

The domestic lounge, in comparison was on a par with most domestic lounges. There was food but not a lot.

Domestic Flight

The domestic flight was a short one. There was only one other person in the business cabin. Getting onto the plane was a faff. Everyone was called at once and it was a bit of a mad scramble. No advanced call for business passengers, frequent fliers, people who needed assistance etc. I wasn't impressed.

The flight itself was fine. No booze, but we had satay. Nice big seats too.

Arrival

Getting off the plane was painless, although while two of our three bags arrived immediately we had to wait for the third, which kind of defeats the point.

So, now for the return, which is more fresh in my head.

return domestic flight

Checking in was a pain. I used the web site on my mobile and wow, it's difficult. At the airport was fine though. Small airport, no lounge. Again, no advance call; just a scramble. More satay.

The Sama Sama

We were on MH4 the following morning so I had pre-booked a room at the airside Sama Sama hotel. It is what it is; a bed for the night. Basic room, a few stains on the carpet but clean. You pay when you get there which makes it easier.
If you do use this hotel (and you should if you want it easy in the morning) do as I did and find out how to get there in google maps in advance. It's on the same level as the Golden lounge but you have to go to the end of the concourse on the gate level (past C1) to get in. The shuttle train runs along this level so you need to be on the correct side of it.

The F lounge

I should have said before that the lounges are a pain to get to. There are very few lifts and the escalators are well-hidden. Whatever you do you'll be doubling back on yourself. If you're lost they're above the train station.

The F lounge is waaaaay better than the J lounge. There's a small restaurant and in general it's a fairly small lounge. Food is decent, but not fantastic. And as someone mentioned on another thread recently, the main lounge area is freezing cold, although the restaurant is fine. Showers and toilets are in a different league from the J lounge.

Boarding

Boarding in F is not great. Security is at the gate, and there's a separate queue for F & J. Just as we were putting our things into the X-ray machine a staff member pushed through with two passengers and pushed their bags through ahead of ours. I thought maybe they had been escorted from the lounge and were our fellow cabin passengers, but they didn't appear on the plane so must have been in J or Y. I was a little bemused by this. Perhaps they were relatives of the staff member.
We were accosted by security as we walked down the tunnel into the plane, who clearly thought we should have been in Y, but I wasn't bothered by that. I wouldn't call the boarding experience premium however. Given there were only five of us in the cabin, they could have made more effort, although previous experience of BA's or QR's handling of F passengers have been equally underwhelming.

First

The bad bit: the cabin is looking a little tired. My footrest was torn and there were signs of age in places. The IFE is also poor but I didn't use it anyway. My wife did and thought it was OK.

The seats, however are great. Nice and big, lie perfectly flat and there's way more room than BA's F seats. A really nice bed, to be frank.
The crew were excellent throughout. Truly first class. The food was also great, apart from the lobster thermador, which was a bit bland for my tastes. Decent bottle of claret.

There was a definite noticeable step above J. The feeling of space was great compared with BA and on a par with QR, although I've only ever flown their old first.

Which leads on to the inevitable comparisons. I'll say upfront that I'm not loaded and while I consider myself fortunate to be able to fly premium cabins, I got a good deal on this trip. Price is an important factor for me.

The standard-bearer for OW is QR for most destinations from London. Would I choose MH over QR? Absolutely. Yes, the lounges aren't as good, but you can still use the QR T4 lounge. The seats are on a par, perhaps not quite as good, but not a huge difference. The food was mostly on a par; I've had good and bad food on QR. A 13-hour leg to KUL plus a short hop to to most of SE Asia is far preferable to me than a couple of 7-hour legs plus a stopover in the "hotel lobby" at 2AM in Doha. A trip to Oz may be different though.

I'd definitely choose MH over BA but that's normal nowadays. Yes, the CW bed is flat on BA, but everything else is worse, including the fare generally. My last 2 for 1 was on BA's 787 to KUL and it was a great flight (in an empty cabin) but I'd rather be on MH's A380.

I do like SE Asia, and for One World travel I'd probably pick CX, MH, QR then BA. I've never flown AY but will give them a shot if the opportunity arises.

Feel free to comment/ask questions.
Apologies for the rambling nature of this post and any typos.