The worst is when you date a super hot chick, someone you'd put in your top 5 hottest of all time, and then you finally get her in bed and she's a cold fish, missionary only, lights off, silent as a mouse....
Unfortunately in my experience,most of the super-hot looking gals that are used to being fawned on/slobbered over by hordes of men fall into this category.They could care less about pleasing you,their mentality is,"he should just be happy I'm giving him a piece."