Being in possession of a new Athlon64 system I took the opportunity of trying out the free trial of the 64-bit Windows XP. As I usually use Windows 2000 I was interested to see what benefits I would get from upgrading, especially after this beta's positive review at GamePC.
The first bit of bad news is that if you want to install onto an SATA hard disk, then you have to hope that there's a driver specifically for your SATA interface to work with x64. Few companies have released even beta drivers, so you have to rely on leaked drivers that have made their way to the only good accumulation at PlanetAMD64 (you have to register, for free, to access their Online Driver Database).
Onto the installation itself, and it's certainly a bit more flash than the Win2K one. It also had drivers built-in for my Radeon 9600XT, so at first boot it had a pleasant hi-res display already set up at my LCD monitor's native resolution.
Again, I had to resort to leaked drivers for various components, but I did get every element of the hardware (ie. LAN, audio, etc.) working.
Now to the software. I was happy to find that almost everything worked perfectly. Mozilla Firefox popped up a Data Execution Protection warning, but you could tell the OS to whitelist Firefox to allow it to work. I only tried one game, the free commerical game Hidden and Dangerous, and that worked well.
There was some stuff that didn't work. The Nero Express software that came with the CD writer stated that it wouldn't work with the 64-bit OS, and that I should buy the Enterprise version. Similarly, the Microsoft Intellipoint software would not install, and so the tilt-wheel mouse lost its tilt.
The difficulty of obtaining drivers, and the lack of general support for software to explicitly work on x64 were enough to dissuade me from keeping the OS for more than a couple of days of experimentation. I have gone back to the safety of Windows 2000.
This contrasts with the beta of Windows 2000, which I happily ran for a six months or longer till the proper release with no qualms. I think that was because it felt more solid. I can't recall any software that I used that didn't work. Even drivers for NT4 tended to work at a pinch. x64 feels like too much of a jump from real-world support, and there doesn't feel like a very large community of users around yet. In addition, the jump in stability from Windows 95/98 to Windows 2000 was so great that any minor inconveniences were easily forgiven. From 2000 to XP x64 there's no similar major leap in functionality or robustness that I could detect.