The font rendering is a dealbreaker for me. I have to use Word periodically for exchanging files with customers where we have zero say in the mechanism. That is, when they say "here's our version of the contract for review before we give you $$$", and it's in Word that doesn't open cleanly in something better like Pages or Google Docs (yeah, I said it and I meant it), then Word it is.

I can't stand using it a moment longer than I have to, and never, ever use it for anything other than this kind of legacy doc compatibility situation. The font rendering is so, so bad that I just can't look at it. If MS ever cared to fix it then I bet that could move their Mac adoption by at least a few percent, which would work out to a nice chunk of change at their scale. But alas, no. We get stuck with something that looks like they took a photo of an LCD calculator screen and downscaled it.