Windows Vista is a bloated pig of an operating system. In fact, compared to Windows XP with Service Pack 2 or 3, Vista requires roughly twice the hardware resources to deliver comparable performance. Even stripped to the bone, with every new UI enhancement turned off and every new background service disabled, Vista is a good 40 percent slower than XP at a variety of business productivity tasks.

The above is no generalization. I've run the tests (repeatedly). I have the hard numbers. (You can see the full range of my results at exo.performance.network, or take in a quick snapshot of Vista/Office 2007 versus XP/Office 2003 results here; see the Test Center Daily for info on the Clarity Studio OfficeBench test script I used for these tests.) Upgrading a user from Windows XP to Vista, without upgrading their hardware, is tantamount to crippling their PC. Think of users with torches lining up outside your datacenter. It's not a pretty picture. 

http://www.pcworld.idg.com.au/index.php/id;1155325152;fp;2;fpid;2;pf;1

gambler: I couldn't agree more, but some Vista features are just almost worth it. like search in the open-browse dialogue. Very nice if you wanto change an icon and has an huge icon database.