The Mac version shows exceptional speed gains across the board, as well.
A cold load under Mac OS X 10.4.9 (running on a tricked-out octocore-two quad-core, 2.66GHz Intel Xeon CPUs-system equipped with an ATI X1900 XT card, 2GB of RAM, and many hundreds of gigabytes of free hard disk space) ran about six times faster than CS2, and when I'd already launched and closed the app before in the same session, it seemed to cache pieces, making the launch more than 36 times faster.
The improvement in start-up time alone may be worth the price of admission. Once you've snailed your way through it, though, it settles into the back of your memory like the 10 miles of construction that blocked your commute home for a few hours. Thankfully, you only have to do it once, maybe twice. There is one performance caveat for the CS3 suites as a whole: it's the slowest, most painful installation I've experienced in years, and that includes bloatware like Microsoft Office 2007. From loading to saving, Photoshop CS3 generally operates faster than Photoshop CS2.