Microsoft unveils Vista upgrade matrix
 

Microsoft has already laid the groundwork for confusion over the release of Windows Vista, with their announcement that the new operating system will come in as many as six different versions. A few of these can be discounted for most users, such as the crippled Starter Edition designed for delivery to third-world markets, and the Enterprise Edition which will typically find itself in the big Fortune 500 office. This still leaves four different skus: Home Basic, Home Premium, Business, and Ultimate.

Anybody have good experience with 95->98 , 98->XP, or ANY other older to newer OS "upgrade" ?

it always leaves traces and makes the OS run NOT optimal, in my humble opinion if you install a new version of an OS, go from SCRATCH. No upgrade matrix needed, no worries. Learn how to make proper backups of your personal files and you're good to go

Upgrades should be done that you bring the old CD/DVD to the shop and then change it into a full version copy.