Peachpit Press has just posted an article I wrote for them comparing Lightroom 2 and 3. Read it if you're hestitating about upgrading from version 2 to version 3.
Or, if you've already made the leap, read it to see just how smart you were. ;-)
Topics covered include improved printing choices (shown in the photo to the right), integration of audio/video, noise reduction, Flickr, and Lightroom 3's very useful Publish Services.