If Microsoft were smart, they would have released the tool for Windows 2000/XP to test for Windows System Performance Ratings in Windows Vista. That way users could test and start upgrading if necessary, so when launch time comes around, their customer base is more ready to accept the new product.
Then again, if they are smart, they will offer massive discounts to upgraders, since I know I’m not alone in thinking that Windows XP may be more than all right for another few years. Not sure I’d pay $200+ for the privilege of installing an even more bloated OS on my computer. It could be a hard sell. It will be interesting to see how they actually do when launch time comes.
Edit [3/16/2006 @ 11:10 PM EST]: According to Engadget they will release a tool for Windows XP users to test with.