Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Granted, you'll have to give it to Microsoft for often being overly optimistic about their accomplishments. As honestly what other company would be pitching a product that's been delayed by almost two years and features nothing new but for 64-bit support like it is a quantum leap from the 32-bit version of Windows XP? In truth the 64-bit version of Windows XP is far from that, at best it is a Windows kernel with 64-bit extensions that works on a handful of systems with a very specific hardware configuration, or to be specific on hardware that has working 64-bit drivers. I say this with caution as the fine print in the press release states that only a 'limited number' of peripherals is natively supported by the operating system, due to lack of a driver. For all of your other 64-bit driver needs you'll have to look towards the manufacturer of your motherboard, graphics or sound card, printer, scanner, etc. to write a 64-bit driver.
Naturally the majority of these manufacturers will not be very motivated to do that unless Windows XP 64-bit gains significant market share or products can be sold at a higher price with the added 64-bit driver support, thus increasing their profit margins. Either way you're lost for drivers unless your hardware is natively supported or the manufacturer gets his act together. Unless this manufacturer is ATI and to a lesser extent NVIDIA you'll be hard pressed to see a 64-bit driver soon, as the majority of manufacturers issue a driver update about twice a year, so you could be in for a long wait. Until then, don't expect your hardware to even squeak, 32-bit drivers are not going to work, and if it isn't supported you might as well take it out.
But there's more, Microsoft has also put into place an upgrade program for current users of 32-bit Windows XP. Unfortunately this upgrade program is only valid for PCs that came shipped with Windows XP preinstalled so most enthusiasts are out of luck. But matters get worse; by applying for this upgrade your current product key for your copy of 32-bit Windows XP will become void, so you can't go back after you've installed Windows XP 64-bit, as your product key will not work anymore when you register with Microsoft. Obviously you won't know whether you would like to keep working with this new version of Windows, and whether your applications and drivers work, after you've installed it.
If that isn't a virtual minefield I don't know what is. You risk to go from a perfectly working system running 32-bit Windows XP, to a non working 64-bit Windows XP and lose your 32-bit Windows XP product key in the process without the ability to go back. To further frustrate end users Microsoft makes very clear that the installation of Windows XP 64-bit will void any support with your PC manufacturer. One free support call will be provided by Microsoft for any installation-related issues whereas additional calls to Microsoft support will be available on a pay-per-incident basis. If that doesn't convince you to steer clear of Windows XP 64-bit for now you must either be really foolhardy or be feeling exceptionally lucky today,