I used to think, "I don’t need Lightroom, I have Photoshop, plus I do a good enough job organizing my photos on my own." While those two statements may be accurate, I was really missing the point. Not only does Lightroom have the basic tools that photographers need on a regular basis, but it also helps me to stay organized and uncluttered.
Since this is the first version of Lightroom I have really worked with, I can’t say much about the improvements from version 2. I can tell you that Lightroom is easy and intuitive to use, and that all of the basic "everyday use" features are easily accessed, including rotating, cropping, spot and red-eye removal, brightness/contrast/curve control, color correction, toning, lens correction/distortion control, vignetting, etc.
Of course, for more advanced and precise editing(intricate masks or selections, multiple layers, etc) Photoshop is still my best friend, but since I don’t do a ton of that I can now accomplish over 90% of my photo editing in Lightroom, in far less time than it used to take me in Photoshop alone. You just can’t beat that.