We've gone into thorough detail about how proguitar works on the software side of Rock Band 3, for better and for worse (you can check out that impressions piece here), so for this review we're largely going to focus on how the hardware feels.
Both times I've tried "Crazy Train" on pro expert guitar, I've had such a visceral feel for what I was playing, It challenged me to play more precisely than I could ever on my own, and the sense of accomplishment was equivalently fulfilling.
This year, Activision's in-house studio Vicarious Visions (known for working on powerhouses like Guitar Hero and Tony Hawk Pro Skater previously) is taking the series in another direction, keeping original Skylanders, the second game's Giants, and adding a new twist in swappable characters.