Windows Vista, contrary to what's circulating around the 'net, will be a complete success. Most people with a decent job would go ahead and buy the OS starting January 29, 2007. With today's hardware, it should NOT be a problem running the slick new Aero interface at full speed. The hype of users switching to Linux (particularly Ubuntu) will soon fade. Mostly these are people who are anti-Microsoft and have nothing better to do than bash Windows, even though they use it themselves -- how hypocritical is that?
Two reasons: Linux does NOT have DVD-ROM playback support "out of the box" and MacOSX is too expensive for the average user. Unless you are a tech geek or an enthusiast, like many, you'll be getting Vista.
Sure Windows Vista will have a slight learning curve particularly to the XP novices, but the grasp will be a snap within a month of using it. Have a novice switched to Linux, the learning curve would be downright huge.