When you upgrade your computer early next year, there are going to be six versions of Vista for you to choose from. Even ignoring Vista Starter, which is for developing countries, and Vista Enterprise, which your office IT guy will shove down your throat, that's still a lot of choices. To decide which one is right for you, you'll have to ask yourself some questions.
If you want BitLocker drive encryption, that's only available on Vista Ultimate. If you want Media Center, that's on Home Premium and Ultimate. Stuff like IIS (webserver), offline files/folders, tablet PC support, faxing and scanning are all only available on the Business editions and Vista Ultimate. Basically, if you want home entertainment, you can go with Home Premium. If you want more business/office stuff, that's Vista Business. If you want a bloated OS, that's
any Vista edition Vista Ultimate.