Adobe just put the CS3 beta out for download on the adobelabs.com website. Registered CS2 owners have full use of it until the actual upgrade comes out next spring or you can try it for 2 days as a non usuer if you want.
I ran a test suite on it on it with my MacBook Pro 2.33 core2 duo and what a difference. CS2 ran the suite in 5min 45sec and CS3 ran it in 3mins 20 sec.
This UB version is obviously going to put the Intel Macs back on the map as far as Photoshop is concerned and the new OS due in April will even improve on that.
Over the past 6 or 7 major upgrades which I've purchased (since PS 3) the full program has been around $600 and the upgrade usually $169.00. The upgrade usually goes back 4 versions (or possibly 3) You can upgrade about every 3 or 4 new ones and then you have to bite the bullet and buy the full vers.