Specifically, the Photoshop and Lightroom teams have been testing our applications since Lion became available to developers. Our teams worked closely with Apple to address/fix issues that were discovered while testing Photoshop CS5. Earlier versions of Adobe Photoshop (CS3 and CS4) were also tested with Lion, with issues that were discovered being documented and addressed by working closely with Apple.
I recommend that Mac users of Photoshop CS2 upgrade to Photoshop CS5 soon in order to be within the 3 versions back in order to enjoy discounted upgrade pricing.
If you do encounter issues not already documented, feel free to report them on our feedback site.
Finally, Mac OS X 10.7 (Lion) includes some exciting new features such as Autosave, Resume, Versioning, Full Screen Mode, and more multi-touch gestures. Since many of these features require new code in order to work properly, the Photoshop and Lightroom teams will investigate which ones make sense to our customers for inclusion in future versions of our products.