I've spent quite a few nights in one. It's well worth the money for lightweight camping. Down here, in warmer weather it is incredibly comfortable....especially in wet areas or when it rains when getting off the ground has a distinct advantage. I never found getting into or out of one a real problem. As a matter of fact, I thought it was an extremely ingenious system to keep the tent sealed from bugs and rain and still be able to get in and out. I would leave my bag pushed more up to the head area, get in, pull the bag down, slide it down to my feet and work the bag up a bit at a time zipping it up as I go. Now, I don't have to get up to go use the bathroom during the night and that might change my opinion of the speed of that procedure but otherwise, it certainly wasn't a deal breaker for me.
By their very nature, they are much, much cooler than an on the ground tent. Most of the time for me, that was a distinct advantage. In cooler months, you have to get your insulation down right but you can certainly get comfortable, at least with the right bag. Adding their cold weather system works well, supplemented with one of the foam/foil windshield reflectors you can get a Walmart, I have been comfortable into the high 20's (that's as cold as I've camped in it). Get the skins too, they work. The new oversized a-sym rainfly is a must too...it's really tough to cook in the rain without it.
It's a lot like my tree-saddle: you have to practice with it and figure out the best way to use it...it's not just a "go out and hang it and it's awesome". But, once you do spend a few afternoon naps in it or even a night or two around the house (where you can always go inside if you are uncomfortable), it fills a niche no tent can, in my opinion.
The main disadvantage is gear storage...but in ultralight ground tents I have the same problem. I bought a second ultralight tarp at REI and use paracord to string my gear and then just tarp it. Not had any problems with that yet and like I said, I had the same problem with small ground tents too.
I will agree that you are far more comfortable sleeping if you can sleep on your back. I like to sleep on my side and can almost get in that position...but I can sleep on my back too so it doesn't really bother me in that regard.
If you buy one, commit to it and give it a full season's chance. I will say you don't see many used ones on fleabay or anywhere else I looked for one before I got one from the factory.
Good luck, if you get it let us know how it works out for you.