I have a 7mm insta-dry rig head to toe. LOVE IT. Yes, as others have noticed, it can be a little tricker than a hyperstretch to put on, but in cold CA waters I'll trade warmth for an extra minute any day. And as noted, it's not truly instantly dry unless you use a towel, but on those multi-dive days on boats, it does dry up pretty quick. WAY faster than other suits.
Two things: (1) It gets easier to put on over time, as the suit molds to your body quite nicely. (2) As someone just mentioned, a spray bottle with a little baby shampoo in water will get you in really quick. I just usually don't bother. (I'm not very hairy, though... if I looked like a yak I might consider something else.)