If you book via Amex, you get full points. I did this last year at Dar al Masyaf. This is very attractive - it is the equivalent of getting about 7.5% of your stay back in freebies. We tend to use ours for free meals or spa treatments at the Jumeirah hotels in London. You can also top up your Sirius points by transferring Amex Membership Rewards points at a 15:1 ratio.

For all of 2011, Amex was also offering '2 nights for 3' or '3 for 4' at all Jumeirah properties. Not sure if this is running for 2012 as well. We had an 8 night stay at Madinat booked (which we ended up cancelling) with 2 lots of '3 for 4' deals back-to-back.

You are right about agents having aggressively lower prices, although there tend to be cancellation fees involved. We found an agent who would give us the agent rates on the hotels without having to book a flight with them, which was attractive as we use Avios or DC miles to get down there. However, we have not yet booked via this guy.

It is also worth noting that if you stay at Emirates Towers in Dubai or the new one on the creek, you get full free access to Madinat Jumeirah, including the beaches and pool. Obviously you are running around in a taxi every day to get over to Madinat, but Emirates Towers is very cheap, especially for a suite - Al Qasr is about £1,200 a night in a suite, Emirates Towers is £400. On a 10-day stay you're looking at £8,000 + taxes saving for the sake of a few taxi rides!!

We did, by the way, get a decent upgrade on our Amex stay - they gave us an Ocean View instead of Canal View at Dar Al Masyaf. However, the hotel did owe us a favour after a problem with our previous stay, which probably contributed as well.

Frankly, the current rates at Madinat are scary. £1,200 for a suite, per night, is not good. Worth noting that, whilst suites are usually excluded from the Amex '2 for 3' / '3 for 4' deals, all standard rooms at Madinat inter-connect via the hallway so you can take 2 of those on a '3 for 4' deal for the same price, but with the discount, as a suite.

Whilst I may be simply tight, I also find - depending on flight times - it is worth spending the first and/or last nights in a resort near the airport, eg the Park Hyatt, or the Crowne Plaza / Interconti complex. If I am flying at 8am or landing at 1am, I don't want to pay for a full night at Madinat when I could crash nearer the airport for literally 15% of the price and then transfer at leisure the next day.