See Adobe's videos one, two, three to see what's new or have a look at the NAPP LR3 Beta Learning Center.
My favorite new features so far (only from the videos, I still have to install it
):- Import presets
- Browse Collections in Develop Mode
- Improved Sharpening/Noise Reduction
- Auto Sync in Develop Mode
- Export Slideshow as a video file (with music)
- Lock library filter as you browse through folders/collections
The Beta version can be downloaded here for free, but please notice that it is not a final release so for critical work it may be better to use LR2..