MOTM

On the Mac, I've been using Performer (then later, Digital Performer) 
since version 1.0 back in the day, and would recommend it highly.

Logic is also very, very highly thought of, and there are levels of the 
program that you can buy into - the baby one, I forget what it's 
called, would be plenty enough for basic audio and MIDI work.

Stay away from ProTools in any version if you want to do any serious 
MIDI stuff - the audio is way there, but the MIDI functionality is not 
the best.

I've never used Cubase, but it seems like a mainly the 
techno/electronica folks and DJ types are the ones using it, and they 
swear by it.

All of these programs, for the serious Pro versions, are gonna be in 
the $350-500 range.

Also, you might want to do a Google Groups search, as this same thread 
was just discussed on rec.audio.pro.

e