I use Noteworthy. It's pretty good for the money. The others are right on the difficulty of playing a piece and having the software figure out the timing. But you can always try a likely note length, listen, and fix it.

Here's a question for everyone: In Noteworthy, I have to tell the computer ahead of time what the time signature (3/4, 6/8 etc)is before playing a piece. Do you have to do this in the expensive programs, or do they figure it out for you? Sometimes when a piece is tricky, the problem is the signature. Recently I was trying out a piece in 6/4 and it was frustrating.