The whole CS suite rules. I was hating Adobe for several years after Illustrator 8. PS has always been great, but 7 had little to recommend it over 6 for my money. But the stuff you can do design-wise with the whole suite - Illutrator, InDesign and PS is great. You have full creative freedom (leave your transparent layers live in PS files, leave all of your spot colors and drop shadow effects live in Illy, then put them together in InDesign and it works without a hitch.) I love them.
Harkyman, what i have noticed at companies from 6 to 7, is 7 seems way more stable…6 used to hanged -at me- doing certain stuff…some of it I had it spotted, but other was more random… Maybe I am to used using rock solid ps versions that I got surprised with crahses even in not press several dozen megs files…
Also , I’m not sure if ps6 has the layer set thing, and I find it very useful, as some glbal actions which are not supported by simple layer linking, you can do if you put them all in a layer set. besides it lets you work better ordered and no need to scroll that much the layers column… Also, it allows better merging in ecrtain situations…
It allowed me also to just duplicate a layer set to have a full set of ui buttons, hide it and recover them at any time…better than merging a file…
also, some more layer modes, if i am not wrong…
and the liquify tool,it wasn’t in 6, was it…i fing it quite useful for 2d morphing animation, and working on textures… for reshaping also…
but yep, don’t justify a purchase, but in a company you don’t waste a buck… 
I use photoshop 5.02. Maybe I could upgrade to CS.
I mean, photoshop 5.0 is good, I didnt like 6.0, when I tried it. Maybe CS is better.
If you’re moving from PS 5 to the CS version, you’ll probably notice a performance hit. 5 is much faster (at least on our hardware).