Date Joined: 12/04/08
Pros: Most reliable and functional operating system to ever come out of Redmond. Good performance and better compatibility on wider range of hardware than Vista. Easier to control or remove unwanted software (just for fun, try and remove - not just hide - the Microsoft games on Vista! Bet you'll take more than half an hour...).
Cons: General software support from Microsoft ends April 2009, though security fixes and paid support will still be available.
Overall Review: You can still get XP after January 2009, but you have to buy Vista Business to get the downgrade rights, *and* you have to have valid media and a valid key (in addition to the new media and key you will have just paid Microsoft for).
Since Microsoft will still be licensing XP quietly through downgrades anyway, the main purpose of this is to allow Microsoft to boast of falsely inflated Vista sales.
I hope this will be the last batch of Microsoft licenses of any kind that we will have to buy - we have switched all servers to open source, moved Exchange to open source alternative that is more stable, converted Office most to the open alternative, but still have some desktop engineering applications that are Windows-only (and actually many of them are XP-only and either are not supported or don't work properly with Vista).