Domenic, I'm one of those carp flyfishers who swear by nymphs, but due to my limited experience, you should take that oath with a grain of salt. My favorite fly right now is a bead head prince nymph, since it's the only fly I've had eaten so far.
On friday I had a few follows on a very poorly tied crayfish pattern, so I'm planning on spending a little time at the vise this week to try and improve the fly a bit in hopes of enticing a strike.
One thing to note: I've only had luck with fish that were actively feeding. From what I've seen, a fish that's hanging in the current, or sunning itself on top is more likely to take off and spook the whole pod than it is to eat, no matter how good the presentation.