Lightroom 3.5 and ACR 6.5 are available on Adobe Labs as release candidates – A “release candidate” label indicates that this update is well tested but would benefit from additional community testing.
New Camera support
Adobe has also included some new lens profiles.
Several bug fixes, including a few for Mac OS 1.7 Lion.
Check out the full list here: http://blogs.adobe.com/lightroomjournal/2011/08/lightroom-3-5-and-camera-raw-6-5-available-on-adobe-labs.html