Lightroom 3, on the surface you wont see a lot of change, where Adobe worked their magic is under the hood.
The new engine for processing noise and sharpening has improved immensely, one of its biggest draw backs since Lightroom was first released, I prefer to do my noise reduction and a small amount of sharpening in RAW format and then complete it in 16 bit TIFF format in PS.
I went back to this image I took in Costa Rica of the of a Chestnut-Mandibled Toucan in the rain forest near Vulcan Areal, I could not believe the improvement in noise reduction that Lightroom was able to do on this ISO 3200 image, detail is maintained while almost completely removing all traces of noise, the image was cropped to about 60% of its original size.
One other big improvement is the lens correction, LR now has lens profiles that can fix distortion and fix it well. I have heard more profiles are coming, so soon you will be able to fix most lens aberrations, a nice feature.
I have always liked LR, but now it really is a great tool to have.
If you have been waiting for an improved Lightroom, now is the time.
Ross Murphy Images In Light