Mike,
If you use RAW files then I'd say yes. Lightroom uses th latest ACR engine which, in my opinion, is ahead the one in CS3.
The best thing to do would be to download Lightroom 3. The trial is valid for 30 days which is sufficient to test and see if it produces improved reasults with your photos and your workflow.
I agree. And while you are trying LR3, be sure to notice whether there are features that you need in CS3 that may not exist in Lightroom (layers, masks, etc.)
I got hooked on Photoshop long before Lightroom came along, and my addiction to certain bit-editing features of Photoshop means that I can't be satisfied with LR alone. But on the other hand, LR is so much more elegant in the things that it does do (once you get used to the user interface, which is very different from PS), that I do as much as I can in LR and then sometimes do some additional tweaking in PS.