I've always praised Adobe for their liberal upgrade policies (if the last release didn't impress you, you can skip a version and still upgrade). In fact, Adobe had one of the least strict policies of any manufacturer and didn't hold you hostage to constant upgrades.
Well, the policy is changing (a bit). Adobe is tightening up its policy on upgrades and applying limits to just how old a copy can be in order to be upgraded. According to the FAQ posted for Photoshop CS3:
Q. If I buy Photoshop CS2 today in order to get access to the Photoshop CS3 beta, will I get a free upgrade to Photoshop CS3?
A. No. The rich feature set and productivity enhancements of Photoshop CS2 already provide a strong upgrade value, and the opportunity to preview the upcoming CS3 release is an additional bonus. In addition, customers who are still using Photoshop version 6.0 or earlier will benefit from taking advantage of a more liberal upgrade policy for Photoshop CS2. Adobe will not offer upgrade pricing more than three versions back on Photoshop CS3. Go to www.adobe.com/products/photoshop/index. html for more information on Adobe Photoshop CS2.
This means a minimum of Photoshop 7 must be owned to buy the upgrade to Photoshop CS3. I agree that this is a reasonable change... but I raise it to you know for you people forced to sit on the fence. I know plenty of people (especially in corporate and education fields) who are constrained when it comes to upgrades....
The bottom line... if you are still using Photoshop 6 or earlier... upgrade now to Photoshop CS2.