I don't understand the bashing of XP64. I have hardware just like everyone else on here pretty much (your typical gamer system on AT: nForce4, Athlon 64, Audigy2 (X-Fi works on 64 as well), Logitech MX518/G5 mouse, Radeon/GeForce video card). The only thing I couldn't get working was my ATI USB TV tuner (because it has no drivers). But there are 64-bit drivers for both brands of video cards (ATI and NVIDIA), and there are 64-bit platform drivers for the nForce MCP and ATI SB480 south bridge/IGP. There are even 64-bit drivers for the ATI TV Wonder Elite TV tuner. There's a 64-bit driver package for the nForce3 platform as well:
http://www.nvidia.com/object/nforce_udp_winxp64_6.25.html
Logitech has 64-bit drivers and configuration tools for most of their recent mice (I know they do for the G5). Creative now has official drivers on their main site for various SoundBlasters (Live/Audigy/X-Fi) on XP X64 platforms. Both of the onboard gigabit NICs on my A8N-SLI Deluxe have 64-bit drivers.
Yes, some of the drivers are beta and/or not WHQL-certified, but does that mean much? We have all had crashes with WHQL drivers and/or "final" drivers anyway. My philosophy is that there is no such thing as a "final" product in drivers. There are always bugs or features that need to be corrected/added.
The sole application that failed to work was Wolfenstein: Enemy Territory, because of a PunkBuster problem, and I only bothered trying one server. PB may have fixed it since. Battlefield 2 with PunkBuster works great (fast if not faster than XP32). XP64 has always feeled much faster to me than XP32. For AntiVirus, there is NOD32 for 64-bit platforms, and I'm sure there are others that work with 64 as well.
I don't know, maybe I'm just lucky or something. The speed advantage was enough for me to add it to my Big O' list of OSes.