I am one of the lucky ones who acquired an advance copy of Guitar Hero: World Tour. I just got it today... Unfortunately, the game has a rather large compatibility problem with the Ion Drum Rocker.
First off, the GH:WT kit has an orange cymbal which is unique to it, and obviously not present on the Ion. As various sites have reported, GH:WT will detect whether or not you have a GH:WT kit or a Rock Band kit, and adjust the note charts accordingly. Well, it detects the Ion as a GH:WT kit, which presents a problem.
The pads all work fine, but when you hit a cymbal on the Ion, for some reason it triggers two different notes in the game (the yellow cymbal triggers yellow and orange, and the green cymbal triggers green and orange). So, every time the orange note comes up, it's impossible to trigger it without triggering another pad at the same time. This causes your multiplier to break every time an orange note comes up, and really kills any chance of getting above four stars in a song (if you're lucky).
I thought that it might be a compatibility problem with Rock Band kits in general, but I hooked up my RB1 kit and it recognized it and removed the orange note from the charts (as I have read here that it would). Unfortunately, there is no option in the settings to change the type of kit manually.
If anyone knows a way around this problem, feel free to share. GH:WT is mad fun from what little I've played, and I'm bummed that I can't use my Ion with it to its fullest capacity. I'm certainly not going back to the RB1 kit. The pads feel like you're hitting a concrete wall compared to the Ion.
Any help/insight on the subject would be appreciated.