LR is basically Adobe Bridge and Adobe Camera Raw combined. Photoshop is a complement to Lightroom, but not necessarily a replacement. It's more of a replacement to Bridge only it doesn't have to load up a bunch of crap for all the other Adobe products that photographers don't want (Illustrator, Dreamweaver, ect). With LR3 going for $70 today, I'd buy a copy if you even thought about using it.