I would say there are excellent reasons to upgrade no matter what field you specialise in, although to my mind the major benefits of CS2 are aimed at photograph handling and manipulation. I find tools like Bridge and Camera RAW, and filters like Smart Sharpen absolutely indispensable.
However, here's the "definitive" answer from Adobe:
Image editing tools for photo retouching - digital photo software by Adobe
If you think you can make use of any or all of these features, then upgrade.