This thread is interesting, considering that I did a solo drysuit dive for my first time today.
I had zero problems with it! It was interesting to be warm at 48 ft with a bottom temperature of 45F. The suit was a Poseidon Unisuit, which is a 7mm neoprene drysuit with an integrated hood. I did not like the valve, as it required you manually push in a button to purge. I was wearing wool socks, sweatpants, and a wool sweater underneath. I had a little bit of leakage up my arms, but I don't think I had the sleeve seals done properly. It also didn't help that the drysuit was about two sizes too big for me. It was a medium-large and I wear a size small wetsuit. My feet were swimming inside the boots. It was not too hard to recover from a feet up position. I had to add 6 lbs of lead to my setup to achieve neutral buoyancy again. I did not like the huge negative swing of the suit and will definitely be investing in a shell drysuit instead.
I tried both techniques for trim & buoyancy : suit inflation only, and combined suit/wing inflation. I did not like running the suit only for buoyancy control. I preferred to have the suit about 3-4 quick shots of air just above "the squeeze". On my ascent, I was very cautious. I stopped every 2 ft to burp a little bit of air out of both my wing and the suit.
All-in-all, it was a good dive though! There wasn't a lot to see, but the added thermal protection was splendid.