PC World posted an article on the shortcomings of the Office 2010 64-bit version

When Windows 7 hit the stands, most advanced users reveled in the fact that 64-bit Windows had finally come of age. In spite of a few driver and application compatibility problems, 64-bit Windows 7 promised faster speeds, access to more memory, improved security, and the ability to run a whole new crop of killer 64-bit applications.

Well, I have seen the future of 64-bit killer applications, and it ain't pretty.

  Beware of Office 2010's 64-bit Shortcomings