32-64

Vista and XP 64 will run virtually all 32 bit apps so there are almost no compatibility issues to deal with.

64 does require special drivers, 32 bit drivers will not install, but thankfully virtually all newish hardware comes with both versions these days. You got a printer or a scanner about three years old or more? Maybe not. Depending on how much trouble the manuf. has gone to to update them.

As for speed - if you have a native 64 bit app, such as Photoshop 4 (64 bit) then yes, it will be significantly faster but if you are running a 32 bit app there will be little or no speed difference. For now there are precious few native 64 apps. That should change in time as we move closer to retiring 32 bit OS. Look for 64 to be the default choice for Windows 7 and for 32 to take the back seat.

The main advantage at this time is the ability to use more RAM. Vista and XP 32 are limited to about 3 gig of usable RAM (they have a 4 gig limit but for complex reasons they can't address more than about 3 gig of the system RAM). With 64 you can use 4, 8, 16 whatever, up to an astronomical number. With RAM so cheap a lot of people are installing 4 to 8 gigs these days which makes 64 very popular now.

XP vs. Vista - XP had a 64 bit version for some time now but driver support for it was slow to come and it never really took off. It has its following for sure and those people will tell you driver support is good enough these days. Vista has excellent 64 bit support and it's getting stronger every day because so many new Vista systems are going 64. Just take a walk through Best Buy. Future support for Vista 64 looks assured for years to come because Windows 7 will use the same drivers.

Vista is working fine now. Stable, fast, and support has finally gotten over the hump it was struggling with at first. The fit and finish of Vista is lacking somewhat and XP still wins the compatibility battle - but Vista is close on compatibility and getting better and it supports DX 10 and the coming 11. Security is improved fundamentally but in exchange you have a rather clumsy UAC cop to deal with. It's a much more beautiful OS to look at. MS did get quite a few things right with this OS after 6 long years of XP.

All in all, for new machines, Vista 64 is the correct choice for the typical gamer/enthusiast profile though there are exceptions here and there.

Vista 64 is the right choice for everyone who can run it...