I would say that I like realistic sex, which by definition is imperfect. I like that hair gets caught on stuff and that it might hurt, and the whole sticky mess that sex is -- no boundlessly stretching, self-lubricating anuses or simultaneous orgasms, ugh. Having said that, I will say that this is not bad sex per se, it's just mimicing (or attempting to) sexual acts in real life much better, which is what makes it hot. Imperfect sex is hotter than perfect, IOW; imperfect doesn't mean the act is unsatisfying or anything short of perfect to the participants.

Then sometimes, I can tell that the author is trying too hard to make it imperfect, especially when it comes to emoting mid-coitus. They might stop for a three-paragraph exposition on feelings and how this imperfect sex means that OMG they might not be soulmates and... gah. Then it's girls-with-cocks fucking, not men. Of course, YMMV.

(I really should not be attempting these things before coffee. :P)