I expect that I will never buy Vista or any future version of Windows. At home I have Win2000 on my ancient desktop, WinXP Pro on my wife's newer but not overly powerful desktop and Win XP Home on my two laptops. I plan on converting all to XP Pro over time, and then stay put. I believe MS has confirmed that they will support XP for another 8 years, which is long enough for me. After that, I will hopefully be able to find a version of Linux that works well enough to become my new OS of choice.
And there is a good chance that any new computers I buy will be Macs. I bought an iMac last year, and it is an absolute joy to work with. Plugged in the power cable, turned it on, and I was connected to my neighbour's unprotected wireless network almost immediately! They just work.
It makes no sense to buy Vista right now, as SP1 is already being planned for later this year, that would be the earliest that I would even consider buying it. Also, if you get Vista installed on a new PC, the EULA does not allow you to install that copy of the OS on a new machine even if you scrap the old one, apparently OEM licenses are tied to the machine not the person.
And I think it was mentioned previously, you have to have WinXP installed on the computer if you are installing the Vista upgrade, you can't simply put in your XP CD for verification. This is a major inconvenience. If you have a hard disk crash you are going to have to install two OS's in order to get your computer running again!
Also, the cost of Vista is ridiculous. You pretty well have to buy the top end Ultimate edition to get all of the networking and media features, which Best Buy Canada has listed for $299 for the upgrade, compare that to $149 for OSX Tiger, or $249 for the FAmily Pack of Tiger (5 licences). Not to mention the hardware requirements are pretty high end. MS recommends 1 GB of RAM, but most reviews I have read say that 2 GB is the bottom end. That is a LOT of memory just to run your OS, IMO.
I wonder if Vista will actually push a critical mass of people to Linux or perhaps Macs?
Finally a comment about business. I work for one of the largest Federal government departments in Canada, around 40,000 employees, and we will be migrating from Win2000 to XP in the next two or three months. Our servers were converted from NT4 to Server2003 last year, and we are moving from Office 2000 to Office 2003. I expect there are a lot of large businesses that are like us, and will not be shovelling out the cash for Vista for many years!