I don't know why so many people are complaining about their SWU. Surely, if you fly enough to be PM or DM with Delta, I would hope/expect that you also understand the importance of reading the T&C's before choosing your gift selection. The SWU T&C on Delta's website is one of the few things that are actually quite clear and well written (well, at least on DL or KL flight, on AF, it's a bit tricker ).

With that said, we've been happily choosing SWUs for the past however many years... Well, it all started when NW gave them out to their PE in the old time. Paying less than 3K a ticket for Europe - Hawaii in business and domestic first confirmed at booking isn't that bad of a deal, imo. Or a trip at about 1,700 USD in business from Europe - US east coast. Or even using them on AF could be good deals too. Of course, with upgrades, you have to be more flexible in order to get upgradable (Z for DL flights) seats at time of booking which I've always managed (well, I only get M if I can manage running the upgrade through at time of booking).

Even if you get a confirmed upgrade when purchasing the M fare, in case of Irrops, you'll find yourself again in Y, so there is a risk. The last time I used an SWU, I was very lucky, my flight the previous day got cancelled (airport closure due to snow), if I'd booked a day earlier, I'd have been OOL.

This is true, but generally in my experience, DL has been quite good with it - meaning that as long as your new flight has availability in business (not necessarily Z class), a call to the elite line can usually get this sorted out. This is for Delta operated flights though as DL obviously can't make AF or KL open up award inventory.

I'm using one right now on a CVG - HNL trip. No complaints from me.

Despite the uncompetitive SWU's DL gives out, they are IMO less uncompetitive than DL SkyMiles. I've never found myself wishing I had 20K more SkyMiles instead of 4 SWU's.

+1, I use EF to check ahead of time but basically I do the same as you. I've never had an SWU expire.

Also, you can redeem them going TPAC but the fare has to be a DL Y fare. Heck, at that point, you mine as well just buy the J fare.

Personally, I think since DL put EC on their int fleet, and as long as I can get a bulkhead seat, I will no longer buy an upgradeable coach ticket when flying to Europe. There's so much leg room in the bulkhead seats, when my feet are fully stretched out, they don't even come close to touching the bulkhead wall.

It can be a Y, B or M fare. I'm not sure about ex-USA but ex-Asia, M fares are well below even discounted BE fares.