First, the good news: like its competitor, Guitar Hero: World Tour, Rock Band 2 allows players to run songs directly from an SD card. No need to scour the fridge! This contradicts what we'd heard previously, but we don't mind because it's awesome.
The less good news is that Harmonix didn't have a straight answer about compatibility between Rock Band 2 and World Tour's bizarro touch-pad-equipped guitar. That doesn't mean it won't work, just that ... maybe they don't know yet. At least Guitar Hero III guitars will probably be available cheaply.
[Screen via IGN]