We were there from Mar 16-24, 2006. I think the crowds are managable in the resorts, except the pools are always packed (at POFQ).
EPCOT & MGM are OK. Not very long wait (except the Talking Sea Turtle in Ecpot for 60 mins).
MK is quite crowded - pls note that we were travelling with DD2 - most of her favourites rides takes at least 45 minutes in queue (no Fast pass - Dumbo, It's a small world, Magic Carpet...) The worst would be meeting Ariel for a picture - we waited in queue for almost 2 hours!!!! She fell asleep and then woke up but not yet her turn.
To be fair, those requires a FP (e.g. Buzz Lightyear)...there are quite managable.
Next year we are going in early Jan and hope that it can be smooth.