64-32bit: servers yes, desktop no.
For servers, that's an understatement. Nothing in the future will work with 32 bit processors. Vendors are all dropping 32 bit support. (MS has already.)
For the desktop... I'm on the "it depends" fence there. If you need to run software that only runs on 32 bit CPUs, then go there. But if you're forward looking, get 64 bit.
With servers, upgrading is a major deal. With a desktop, who cares? For a desktop, you unplug it... AACCKK! That would never happen for a server... I think you get my drift there.
But even for the desktop arena, I see a lot of vendors going 64 bit now (component vendors included).
I like to buy for tomorrow, because that's always where the computing market is. But, if I need something that won't go there, it's a no brainer. Stick with what works.