Here's a few key things that irk me about Vista...
Hardware Compatibility
You can run Vista on just about any computer, but only one package. Windows Vista Basic. So, that means no 3D Aero graphics, live animation along the taskbar, smooth streaming graphics on your desktop and other key features that make Vista good. So, in order to get the full aspect of Vista, you have to get preferably a new computer overall or a new video card with a crap load of new memory. Either way, by updating to Vista, you're not only throwing down money for the upgrade disc, but for other components that you need in order to enjoy the full experience. Blasphemy is too small of a word.
Aero Graphics & Battery Life
Um, they kill it. If you want your Aero graphics, then you gotta sacrifice your long business trips. Your battery simply will not hold up. Good ol' Microsh*t.
User Account Protection
Just about every single file you open and/or download goes through a cleansing process that takes up too much time and takes too much of you, the user to endure through. Even administrator accounts have to sit through useless Q&A's with the UAP helper.
The Instant Off Option
It takes a screenshot of what you're doing and shuts down your computer preventing it to steam up your backpack or what have you when you're on the go. Sounds nice, but more often than not it totally forgets what you were doing before you shut it down. Yet, Microsh*t is saying they totally fixed this problem, and is one of the key features of Vista they are truly proud of.
and...
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[*]No support for DVD drives lacking firmware region coding.
[*]New monitor needed to view Hi-Def content.
[*]Vista will encrypt hard drives by default.
[*]Vista may shorten the life of flash memory.
[*] Drivers have to be signed for x64 versions of Vista.
[*]Vista won't work with many graphics cards and will remove games developers' ability to cater for older systems.
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I'll stick with my XP.