He is a champion that requires the player behind him to play perfectly, or he falls apart. His early game is not that great. Yeah, he has a guaranteed crit, but he better execute you with it or he's royally boned.
He has no escapes, no reliable cc, and like all adc's, he is very item dependent. I guess trading can suck if he waits for his crit and nails you with it, but if he does half the time you can just go after him while he reloads; he can't do anything to you for quite a while if he runs out of ammo. I really don't see him doing well outside of higher level/pro streams, so if you're losing bot lane to him in the early game, you're probably not playing the match up correctly.