As I first noted in my hint on Living With 64-Bit Windows, about the only disadvantage of using a 64-bit Windows system is the lack of drivers for some devices. I've been amazed at how certain vendors seemingly can't be bothered with x64 drivers. Whenever I've asked, the justification I've received (typically from some brainless marketroid) is that x64 has "no market share."
If you're stuck in the "I'm missing a key driver for my x64" swamp, cheer up! It looks like relief is finally in sight. And that relief, believe it or not, is coming in the form of Windows Vista.
What does Windows Vista have to do with getting x64 drivers you ask? Well, starting with Windows Vista if a company wants to logo an x86 version of their driver, they'll have to also logo an x64 version. That's right! According to the plan (which is, of course, subject to change before Vista release) you can't logo just a 32-bit driver anymore. You can logo just a 64-bit driver. But if you want to logo your x86 driver, you'll also have to be able to logo a driver for x64.
I had heard rumors to this effect, but I didn't believe it until I found the text buried in the 300+ page document Windows Logo Program Device Requirements for Windows Vista Client and Windows Server code named "Longhorn," Version 3.0, Revision draft 0.80, March 10, 2006 that's on Microsoft's web site. I won't quote the text here because there's a long stupid legal agreement at the beginning of the document that seems to imply I can't. But, you can check it out for yourself.
Go download this executable: http://download.microsoft.com/download/d/e/1/de1e0c8f-a222-47bc-b78b-1656d4cf3cf7/WLPSuite_v3_08.exe -- When you run it, it'll unpack some files. Among those files, you'll find the document referenced above. Look for Device Fundamentals logo requirement 14 (search for the string "devfund-0014" without the quotes). And, voila!
This reminds me of the old "if you submit a driver for Windows, you also have to submit one for NT" gambit from back in the early-mid 90's. That (and binary compatible miniport drivers) helped NT gain critical device support, and thus market share. The rest of that story is history.
So, it seems that once Vista ships, we'll never have to worry about support for most ordinary devices again. And it seems that the x64 will be well on its way to mainstream status.
It's about time.