Couple of days ago I've installed Windows Server 2008 R2 Standard on my playground box: an OptiPlex 740 from DELL.
Unfortunately, the machine runs extremely unstable: freezes, becomes suddenly terribly slow, doesn't respond on network access requests.
Guessed the problem are drivers, I was looking around for some updates from DELL and found new BIOS version (I had 2.1.8, the new one is 2.2.2).
After update the strange effects didn't apper yet. Let's wait...
Anyway: if you are going to setup WIndows Server 2008 R2 on your box - update BIOS before setup and enjoy Windows Server 2008 R2, the first Microsoft Server Operating System available only as 64-Bit OS.