via StreamOfNath on RockBand.com Forums

Wow… based on what I had been hearing through both unofficial and official channels (including one very reliable source this week in New York), it didn’t sound like the Rock Band 2 patch adding in wireless mics and Rock Band Network capability was going to be here this soon… but here it is!

UPDATE: Here’s the official list of additional features/fixes from Dan Teasdale (Rock Band 2 Lead Designer):

• Rock Band Network Audition Mode. Available from the “Extras” menu on Xbox 360 versions of Rock Band 2, members of the Rock Band Network can now upload songs from their PC’s and audition their songs using our suite of song audition and testing tools. Currently in closed beta, the Rock Band Network will welcome authors to open beta in the coming weeks! Find out more at http://creators.rockband.com
• “Sort by Stars” in Quickplay. If you hit the “Sort” button on the Song Select screen, you’ll come to a brand new sort that orders songs by the star ratings that you’ve achieved on each song. Each star rating gets a category, as well as an “Unplayed” category for songs that don’t have a star rating recorded. Finally, you can record your progress towards gold starring every song in your library!
• Background Downloading in the Music Store. Purchasing songs from the Rock Band Music Store now no longer requires you to wait for a song to download before you can download another song. You can now queue up downloads to your heart’s content, which is going to be incredibly handy with some of the amazing DLC that’s coming out over the next few weeks and months.
• Xbox 360 Wireless Microphone Support. Rock Band 2 now supports Xbox 360 Wireless Microphones, like the Lips microphone. Finally, you can now have a fully wireless Rock Band experience!
• Chord HOPO improvements: If you’ve played The Beatles: Rock Band, you’ll notice much more robust handling of chord hammer-ons and pull-offs. This patch implements those changes in Rock Band 2 to provide a more natural chord hammer-on/pull-off experience.
• Velocity Sensitivity on Ion Drum Kits: Ion Drum kits now support velocity sensitivity in both drum fills and Drum Freestyle mode.

Sean provides additional clarity below:

Regarding the Star Sorting functionality – The intended functionality is this: there is a new “Sort” category on the Song Select screen. This sort orders your songs by star ratings in a series of categories based on number of stars achieved, including an Unplayed category. It should be noted that all songs are listed as “Unplayed” when you first get the title update.  Some people have noticed that after playing a song it remains “Unplayed”. We are aware of this issue and are looking into a way to fix it. In the mean time the workaround is to beat your previous high score. If you get a higher score the song will appear properly in the “Sort by Stars” categories.

Also according to Sean, the PS3 patch will be coming later due to extra development time.  The Wii version of Rock Band 2 unfortunately will not be getting the patch as the console does not allow title updates for games.

[Thanks to @chrisallor for the heads up!]