In case anyone is in the same position I was in, here's my little "Ion drumkit isn't right for me" story:
I was very much considering picking this thing up for it's ability to convert into a real electronic drum kit, but once I researched it and priced everything out I realized that the Alesis Ion kits are on the low end of the quality spectrum, and I could nearly get a nice quality name brand Roland kit for the same price.
Not wanting to spend so much, but wanting an electronic drum kit that I can play in my condo without being attacked by neighbors, I decided to build my own DIY kit. For under $400 total, I have a fully functioning 5 piece kit with Hats, two Crashes, and a Ride running through a Roland TD-3 module. All pads have mesh heads (which is the expensive professional option) instead of being just rubber blocks. Real kick pedal, real high hat pedal... the works.
I know it's not the same as being able to hit in-game notes, but yesterday I was setting Rock Band on Training Mode and playing my DIY kit along with that. Because the game doesn't play the drum part unless it registers hits, it basically makes it a Drum Karaeoke machine for me to practice and play along with. And when I wanna kick some butt online, I just saddle up to the ol' 4 colored pads.
Just another option for those who wanna get into real drums but aren't sold on the Ion.