Word, Excel, and homegrown VB6 apps don't benefit at all from a move to 64-bit.
As much as I'd love to be running the latest and greatest, there really is no business case for the upgrade. What I would like is to be able to develop in VS11, but I guess that's not going to happen.
If you don't accept security as a business case (and you probably should), then the only driving factor is likely to be app compatibility. So VS11 not running on XP is merely the first in a line of reasons to upgrade.
And if you're running a VDI infrastructure already, you're actually in a much better position to handle upgrading in a rather more seamless fashion.