Adobe Lightroom 2.1 is mainly a bug release with additional camera support.
New cameras: Canon 1000D, 50D, Fuji FinePix IS Pro, Kodak EasyShare Z1015 IW, Leaf AFi II 6, AFt II 7, Aptus II 6, Aptus II 7, Nikon D700, Nikon D90, Nikon Coolpix P6000, Olympus SP-565 UZ, Pentax K2000 (K-m), Sigma DP1, Sony A900.
Many of the performance and stability bugs have been fixed and this latest update is running much more smoothly than the 2.0 release.
It was first released on the Adobe Labs site for additional public testing before official release, so it’s a pretty safe update. Additional bug fixes were introducted after the beta program, so do update if you used the beta.