I know, but it doesn't have all the capabilities that photoshop does. For example (a very important example in my opinion) lightroom does not utilize layers.
Yeah, and Lightroom also doesn't have the price-tag that CS5 has, did you stop to consider that?
Photoshop is more geared towards photo manipulation, being able to add text to images, use layers/masks, make composites, etc.
Lightroom is more geared towards adjustment sliders and histograms, while it still gives you all of the necessary tools to make a good photo an outstanding photo. It also gives you easier access to your EXIF info (as far as I know). I would suggest Lightroom over Photoshop for a photography enthusiast.
They are both IMAGE EDITING software. They take an image SOOC and they change the appearance of it, subtly or drastically... Regardless, they both are used for image editing.
I am a photographer and graphic designer. I use Photoshop to make mockups for special sections in the newspaper I lay out, and I use Lightroom to process ALL of the images that I take for the paper, and only Lightroom. I've found it useless to bring them into Photoshop for most purposes, other than to convert to CMYK.