EZDrummer
 

Seen this program on the net but before I spend $100 buying it I need to know if it's any good. Does anybody have this?

I've seen many people say good things about it over on Cakewalkforums. A lot of people use it in conjunction with their music sequencing software. Another one is BFD, but I seem to find more references to EZdrummer.

I haven't used it, but the stats seem to speak for themselves.
You may want to see if you can download a demo version and give it a test drive.