It will be the first system using DirectX 10, which is supposedly a big step forward in graphics technology. Halo 2 will be released ONLY for Vista, as an incentive. Also, Flight Simulator 2006 (aka FSX) will be released, and will unleash the next generation of simulated flight.
Microsoft has received much criticism due to excessive focus on visual features, rather than performance, within Windows Vista. Also, the price of Vista Ultimate is expected to be in the appauling $200-400 range, which may possibly worsen Microsoft's low sales (due to the XBOX 360).
Recently, they have received immense criticism for Microsoft's security and privacy settings, and have been accused of making spyware, known as the WGA (Windows Genuine Notification). Unfortunately, this technology will be integrated and unremovable from Vista, which also may decrease their popularity and sales.
System requirements also pose an issue to many consumers, due to their lack of the latest technology, which is QUITE out of reach to most, due to price. Microsoft recommends Vista users to have Dual-Core 64-bit Processors, and at LEAST 1GB Dual-Channel DDR2 Memory, and PCI-Express Motherboards. These features are still extremely expensive at this time, and with people not having access to it, Vista will have dramatically less copies sold.
Pirated copies of Windows Vista will not function, due to "genuine-technology", so millions of users from third-world countries may be stuck with Windows XP or earlier versions.
Last, but certainly not least, Internet Explorer 7 will be released with Windows Vista, and is said to be "much improved, secure and optimized", however many users will not be using it due to IE's history and lack of trust for Microsoft's browser.
Joe: IE 7 is supposed to be really good!
Tom: I don't give a s**t, Firefox is better-
Tom: Shut up!
Joe: Ok.... (sad) Anyway, I can't wait for FS2006, FS2004 Sucked!
Tom: I know, but your computer isn't good enough, and you can't afford Windows Vista.
Joe: Ok.... (crying) What about Halo 2?
Joe: Ok.... (weeping)