Improved chord hammer-on/pull off notes, taken from The Beatles: Rock Band's better handling of the feature, have been patched into Rock Band 2 as part of an omnibus update that became available today.
Additionally the update enables support for wireless microphones and lays down an "audition" feature you may use when the Rock Band Network enters its open beta.
When "Audition Mode" goes live, RBN members will be able to "upload songs from their PCs and audition their songs using our suite of song audition and testing tools", according to the official Rock Band Forums. Currently, Rock Band Network is in closed beta and the game will tell you 'To enter Audition Mode, you must be signed into an Xbox Live enabled gamer profile that is a member of the XNA Creators Club and connected to Xbox Live.'" Harmonix says the open beta will commence in the coming weeks.
Meantime, gamers will find improvements to the hammer on/pull off tricks in guitar play. The forum says these improvements were brought over from The Beatles: Rock Band, which featured "much more robust handling" of hammer-on and pull-off.
Other upgrades: In the sort menu, you may now arrange songs according to the star rating you've achieved in each of them. Unplayed songs will be grouped accordingly. This helps players chart their progress toward five-starring every song they own.
The game will also support wireless mikes, such as the Lips microphone. Ion Drum Kits now have velocity sensitivity in both drum fills and freestyle mode. And most conveniently, background downloading in the Music Store has been enabled, so you no longer have to wait for the complete download of a purchased song before moving on to another.
As for the PS3, Harmonix' Sean Baptiste explained that patch is being worked on and awaiting its certification process with Sony.