Depends on the skinsuit, I have one I've worn for 12s and 24s with no issues but I have another I wouldn't want to wear for more than a couple of hours.
@bananaskid has done a couple of tcrs in one, as have others.
Toilet access is also an issue, but maybe not much worse than bib shorts.
I wouldn't say any skin suit I've worn has been more comfortable than good jersey and shorts. The reason I'd wear one is for aero gains not comfort.