I have XP and Vista running on various computers.
First Tony, Dell sucks. My opinion, but their support and staff suck.
I use HP or Sony.
Vista is okay. Like Theo said, there are many annoying pop up features that need to be disabled. There seems to be a prompt for every click and command asking you something or wanting more information. Straight out of the box, it is my understanding that all Vista is like this.
I am notorious for disabling the hell out of pre-installed programs on a new computer. To me, that is job number one. But Vista has all of this in its guts and you will have to know where to go to disable them. There are some tweaks available online. This annoyances slow down productivity tremendously and can be bothersome while you are doing something. Auto updates are the same...disabled. Usually there are so many programs running in the background that you are unaware of that they can slow any processor down and rob memory.
With that said, I now feel right at home with both Vista and XP. New products were supposed to stop shipping with XP but there have been so many complaints from customers that MS has decided to extend shipping until March.
As for Dell, man...stay away. I had nothing but nightmares with my one and only dell product and their tech support and staff.
Unless you need one this very moment, I would look at Office Depot or Staples the day after Thanksgiving. Not only do they have some incredible deals but they usually have some unbelievable unadvertised specials. You might also find yourself considering on of the souped up Toshiba, Sony, HP or other brand laptops that are a desktop replacement.
For some torture, I am going to take one of my older models and load Linspire, RedHat, SuseLinux along with XP. I mistakenly erased the entire hard drive (after transferring everything). It is still a superb computer. I thought, what the heck...lets partition the hell out of it and load all these other OS's up. I haven't done it yet. But I thought I would try all these other OS that people have recommended.