After messing with Lightroom 3, it is snappier than Lightroom 2 in just about every facet. It comes with a Flickr plugin and connects to Flickr and the images stored on the site in your account, which is much nicer than the plugin for LR 2 which only lets you upload. Like LR 2 it has a slideshow pane, but it lets you export a slide show to a movie file which you can put into a digital frame or any device that plays movies, there is enhancements to the noise removal as well as a panel to add grain like from the film days.
Its still in Beta and probably won't see retail shelves till mid 2010, if your in the market for Lightroom2, I might wait or contact adobe to see if you can get the upgrade for free if you buy lightroom 2...