As with the Adobe Camera Raw plug-in for Photoshop, LR3 adds automatic, profile-based lens corrections to address distortion, chromatic aberration and vignetting. At least in the final release I looked at, it had a pretty meager selection of lenses, and was missing some important ones, like the Nikon 18-55mm kit lens. And in cases like this, I was able to get much better results (for CA, at least) with manual tweaking. It's also a bit annoying that the profiles don't tell you what settings they're automatically applying. Adobe is still tweaking its profiles, and we expect some slipstream upgrades subsequent to launch.