I too would heartily recommend Jamstix. No doubt that it's tough to learn, but once you learn to use it, you'll never need another drum program. And (as someone already mentioned) you can use Jamstix to drive any other drum kits you own. If Ralph (the owner/creator of Jamstix) would make a good series of video tutorials for Jamstix, I think this could become the most popular drum software. And I don't think anyone mentioned that you can get the basic version for free: