I’ve just read a great article over on the xequals+blog which supports how I’ve been working with my photos for a while now.
Their basic premise is that if you shoot in RAW and have Lightroom, then you shouldn’t really need to use Photoshop more than 10% of the time.
Lightroom is designed to adjust pixels in a non-destructive way… Photoshop is designed to manipulate pixels by altering and moving pixels in a rendered image. So in a sense, Lightroom output is as pristine as a print made directly from a frame of film while Photoshop output is like taking a retouching brush to the print.
Of course, as they point out, the first thing is to get the image captured in camera as perfectly as you can so you’re doing as few amends as possible.