One of the requested features for Rock Band 2 users has been implemented with a title update on the Xbox 360, allowing support for wireless microphones such as those included with Lips.
The Rock Band forums divulge all of the details, including background downloading of all songs purchased from the music store, and the ability to test created songs from your PC. The same updates will be available on the PS3 soon, possibly by the time you read this, as the patch works its way through certification. Wii owners, well, that can’t be patched because the system doesn’t allow retail software to be fixed. Sorry.