For those of you out there pondering whether you should rush to the store to buy the Windows Vista Upgrade or purchase a new computer with it preinstalled, I offer you the following advice: Don't do it.
I think the biggest reason revolves around security. When Windows XP launched back in 2001, it was touted as the most secure Windows yet. In retrospect, I can safely say that it wasn't. Security holes, viruses, worms crawled all over the place as if there was no security at all. Granted, this came about before Microsoft set the firewall to be turned on by default, but the reason I bring this up is the fact that we've heard them make claims time and time again concerning their security, only for someone to come along and prove them wrong—especially in the first couple of years.
Another reason for not upgrading is the user interface. Sure it looks all bubbly and Applesque, but it takes quite an expensive rig for it to even work well. I've got a pretty nice machine myself and was greatly disappointed that I couldn't run all the bells and whistles that Microsoft said I'd be able to run. What was especially disappointing is that those 'extras' that I could use ran very slowly. Don't be hypnotized by the slick interface just find out that your computer can't run it.
DRM. For those who don't know what that is, it stands for Digital Rights Management. This basically boils down to how multimedia files can be played on other electronic devices. For example, if you record TV or music or anything that anyone else can put DRM on, don't expect to be able to play that content on any other device. Whether that be on another computer, a digital music player, or DVD player, Microsoft fully supports taking away your rights to fair use for digital content. Vista will come with all the locks on how you legally use your music, TV, and movies.
All these points aside, you will eventually end up with a computer that has Windows Vista on it. It's inevitable. However, I would encourage you to not follow the masses of mindless zombies that will get it as soon as it comes out. I would give it at least a year. This way Microsoft can work out the kinks, greater advances in hardware will occur, and maybe some workarounds will crop out to those that want to bar you from fair use of digital content.