Comment by objclxt

I'm prepared to give Microsoft the benefit of the doubt here, and suggest that Office is a bit more complex than your average user-land application. I suspect a lot of the code is either quite old or low-level, to a much larger degree than a typical app. It's not just Microsoft - think about how long it took Apple to migrate iTunes from Carbon to Cocoa, or Adobe to get 64 bit PhotoShop on the Mac.