X-Play this evening, and showed gameplay similar to that of Rock Band Unplugged. Dispensing with peripherals, the controller-based gameplay has dexterous finger gymnasts cruising down a note highway, hitting blocks and switching between instruments for maximum scores.
The title will launch with 25 tracks, but the real coup is that the game can access the current Rock Band library on your console. The game also has access to the Rock Band Music Store for more DLC, meaning there are potentially over 3,500 tracks to import. As a bonus, the 25 songs that are bundled with the game are playable in Rock Band 3.