LR vs. PS
Hey Chris!
I've been using PS for quite awhile (anyone remember PS2? :} [no, not a keyboard!]), and have been using LR since the beta. Here are my observations (take with a few grains of salt, please!)
LR: This is your library and IMAGE maintainer/editor. I use LR to bring in and color correct my full image; most of the features in LR operate over the entire image, not just a portion of it. So you can interactively and non-destructively change white balance, color saturation, etc, etc, in LR. The nice thing about LR is id does NOT destroy your original image! And the library functions are wonderful to have, allowing you to select images based on key words, perception level (you can flag them as to how well you like them, etc).
PS: This is your image editor. With it, you select areas to "adjust" to your liking, change/mix/remove items from your pictures, and in general can do just about anything to your image. It's not as flexible for RAW as LR (you have to use a RAW tool to load the image into PS, which limits what you can do interactively). However, it is a fantastic pixel editor. Don't want that tree limb growing in that place? remove/move it!
Another place where PS excels: plugins! PS has quite a few plugins for sharpening, noise filtering, etc. These are very useful when printing, for example.
So, to summarize how I see the difference between the two: I use LR for manipulating my library of images and changes to an entire image, and I use PS for manipulating parts of the image or for fine tuning when getting ready to print or adjust the 'look' of a single image.
Hope that helps! Good luck!
Jason