The challenge has been laid down - why upgrade to Windows Vista? Both Bill and MomGuy are asking the question (amongst others). The difficulty in answering this question is that there is no single answer that satisfies everyone. As Mitch correctly points out, a killer feature for one user might be a non-event for another.

Some users are simply going to get Vista when they get a new computer. At the other end of the spectrum, major enterprises will mostly only upgrade when the lifecycle of their exiting platform ends, or they are experiencing major productivity issues with their existing platform and need to perform some kind of refresh anyway

Each day or two from now on, I'll try to highlight some of the new features and technologies in Vista/Longhorn Server, starting with security and system stability. Hopefully people can see enough useful things within these posts to dispense with the idea that Vista offers nothing of great value.

Our first post will be on service factoring within Windows Vista, and how that will help with security and system integrity.

PS: Bill does make some comparisons between XP and Vista. Certainly on the speed front, Vista isn't going to be faster than XP on current hardware. No new operating system from Microsoft has been faster than its predecessor on current hardware. However I wager that Vista will perform well on future hardware, in the same way that XP will better on current hardware than Windows 95 does (multi-processor support, 4GB RAM support, NTFS support and so forth).