We've got the final game and a keyboard. How does it fare?
http://www.nintendoworldreport.com/impressions/24343
The keyboard in Rock Band 3 feels like a brand new instrument, and that's the highest compliment I can give it. After spending several hours with Harmonix's latest instrument addition to the series, I'm very impressed with how it feels and what it adds to the game.
The regular keys are extremely similar to the guitar and bass charts, with five colored highways populating the screen. They are so similar, in fact, that you can use the keyboard for the guitar and bass parts, and the keyboard even comes with a strap that can make it a keytar. The Rock Band keyboard also has a slide pad that acts as a whammy bar and an overdrive activator on the handle. While the normal keys don't bring anything truly innovative to the table, the experience is solid and differentiates itself enough from the other instruments.
However, switch that bad boy over to Pro mode and you have yourself a revelation. Thanks to smartly implemented training tools and a gentle learning curve, you can legitimately learn how to play keyboard using this game. Albeit you're only using a two-octave keyboard (unless you wait until November for the MIDI Pro Adapter so you can use your own keyboard, but even that will only use two octaves as far as I know), but it teaches you how to play keyboard. I haven't experienced the other Pro instruments, but if they're half as good as Pro keyboard, then they're probably awesome.
When you hop into any song, you'll be presented with a set range of 10 keys at the outset. It varies from song to song, and as you up the difficulty, the range will jump around, effectively making the whole instrument available. It's hard to get into at first, but I was able to nail Easy songs in no time, and I've only ever played "Chopsticks" on a piano before. I'm currently working on the Medium difficulty level, and I'm having a blast.
Much like how my ultimate drum-playing goal in the original Rock Band was to beat Rush's "Tom Sawyer" on Expert, my goal for Rock Band 3 is to beat "Bohemian Rhapsody" on Expert Pro Keys. I would bet against me, but with the tools at hand, I might be able to pull it out in time. That is the magic of the keyboard in Rock Band 3. The rest of the game is great, too. We'll have a full review up in a few days.