The kit is awesome and very customisable. I used to miss beats on rock band 1 drum or sometime get cross beats as they are so close together, but not anymore with the ION kit. The pads on these are firm but give you a great bounce hence making it easier for drum rolls, plus I haven't missed any or many beats on the pads now :-)
The cymbals are must have addition too. Albiet they are a bit noisy, and initially you may get double hits or no hits sometimes. But all these problems can be eliminated by proper setup of the cymbals. Check out the rockband forums for a thread called "Cymbal help" - something like that.
Lastly, the pedal is really really good. Take much less force to hit the pedal, but it is still weighty and has a good natural bounce to it so you can get the double bass much easier than in rock band 1 pedal. You can also get some Destroyer pedals to replace the one that comes in the box which is sweet.