Lightroom is more of a program that helps you organize your photos, and also providing basic but powerful tweaking tools that let you change coloring, exposure, contrast, etc. If you've ever used Apple Aperture it's basically like that. Photoshop CS4 of course can do all those things and much more, so that is why I continue to use PS over anything else. Head on over to adobe.com and download some trials and see what you like best.