Perhaps I am wrong, but I do not see any suggestion that Vista supports 64-bit computing.[{POST_SNAPBACK}][/a]
There is a 64 bit version of Vista, but applications that support 64 bit operation are few and far between. Indeed, there was (eventually) a 64 bit version of Windows XP, but it was a white elephant because of lack of drivers.
Driver support is still an issue for 64 bit Vista. 32 bit applications will run on 64 bit Vista, but you must have 64 bit drivers for your hardware, and 64 bit versions of some programs that interact with the OS at a low level, such as antivirus software (the situation is not as bad here as it once was; I use Kaspersky AntiVirus for Windows Workstations, which now has 64 bit support), backup software and defragmentation software.
Things are slowly getting better in 64 bit Windows land - for example, Wacom tablets now have 64 bit drivers, and a lot of modern mid to high end hardware also has support. If you're buying a new machine and want 64 bit Vista support, it's best to buy the machine with 64 bit Vista installed - that way, all components have to be 64 bit compatible.
Many of us will lose at least some existing hardware switching to a 64 bit OS. The real nasty with 64 bit Vista, as I understand is, is that it's not just a case of the hardware companies producing Vista drivers - you can only install them in 64 bit Vista if they are correctly digitally signed unless you're prepared to press F8 at every boot and choose an option to load unsigned drivers.
I'm pretty fortunate in that all three of my printers have Vista 64 bit support (HP Photosmart Pro B9180, HP Color LaserJet 3800dtn, Canon i865 - not that that gets much use now).
My USB bits and pieces are a much more mixed bag. Most seem to have drivers for Vista 64 bit - my Wacom Intuos 3 tablet certainly does, as does my Dymo label printer. Card readers and USB hard disks don't need drivers - they use Windows' own HID driver. My keyboard and mouse (if I moved them to a future Vista box anyway) are Microsoft products, so no problems there. My APC SmartUPS should be OK; the hardware driver on Windows XP is a Microsoft one anyway and I suspect this is also the case on Vista, whilst the higher level software is now available in a Vista compatible version.
At this point I begin to hit problems. My HP ScanJet 7450C scanner only has a very limited WIA driver for Vista anyway - be it 32 bit or 64 bit - I'm a bit ticked off at HP for dropping support for what was an expensive scanner so quickly. My Monaco OPTIX XR Pro monitor calibrator may work - there is a Vista driver for the hardware (for both 32 and 64 bit), but I'm not sure how well the software works under Vista. My Philips webcam is ancient and there's no Vista drivers at all, though that's not a great loss as webcams are cheap. My Bluetooth dongle may work with Vista's own Bluetooth stack - if not, that would also need replacing, though I am thinking of tossing it in favour of a Bluetooth 2.0 one anyway.
In fact, I seem to be in the same position with my peripheral hardware whether I wanted to use it with a new Vista 32 bit machine or a new Vista 64 bit machine (I'm not intending to upgrade any of my current computers to Vista - if I do go to Vista, it will be on new hardware). I'm not sure many will be so fortunate.
However, the big question is whether it's worth the pain of going to a 64 bit OS. There are gains with a 64 bit OS in terms of being able to have more than 4GB of memory in the system without hackish solutions like PAE, also there are some extra registers, but they're not going to help application like Photoshop and Lightroom. The drawbacks in terms of driver support have previously kept many users with a 32 bit Windows OS, and I suspect many people running Vista are running the 32 bit version because it's the more conservative choice.
At the moment, most of the software we'd want to run isn't available in 64 bit versions. 64 bit Windows can run 32 bit applications. Lightroom, Photoshop and the other CS3 applications are all 32 bit - for interesting comments on 64 bit Photoshop see [a href=\"http://blogs.adobe.com/scottbyer/2006/12/64_bitswhen.html]Scott Byer's blog[/url]. Do we really need the availability of more than 4GB of RAM in Photoshop at the moment?
For most photographers, gains like new motherboard / processor architectures with better memory bandwidth will show greater improvements in performance than a 64 bit version of Photoshop would at the moment.
64 bit desktop applications will happen - but it will probably not be for a while yet. It will probably be the next generation of operating systems before we start to see 64 bit desktop applications.
David