I just got RB3 on Tuesday and have got to say that it’s different enough so far that it caught me off guard
One of the points of all the previous Rock Band games (and Guitar Hero games, for that matter) has always been to play gigs for cash to purchase new gear, songs, characters, etc. With RB3 there is no currency. You don’t purchase new gear. You have what the game calls “goals.” Think of goals like achievements. As you reach goals (which are pre-set by the game), you can unlock new outfits and instruments.
It looks like you still play to get fans like in previous versions of RB, but as they were previously tied to cash (I believe, don’t quote me), this is another change. You are still limited to certain venues at the beginning, but as you gain fans you can “level up” the band and reach goals, unlocking new things.
Another change I noticed as a casual player is that playing on medium has noticeably more of the dreaded orange button. In previous versions, you had a couple songs that would use it once or twice. I’ve only played for a couple hours since I got it, and it feels like almost every song has it in there at least once. I see this as a good thing, since the orange button is what was keeping me from progressing to the “hard” level, but I could see how people who just play to relax and don’t want to worry about orange could find it annoying.
I purchased the keyboard controller with the game, but I haven’t played with it much. It feels pretty sturdy and they seem to have thought out the differences between “traditional” and “pro” mode controls fairly well. It’s a bit of an adjustment for me with no previous piano / keyboard experience to get used to following the keys on the screen with my right hand instead of my left, but I guess that’s just a part of the learning curve of the new instrument.