I too am absolutely baffled about this. I would buy office 2013 if they fixed this issue. But until they do, it's simply unusable. The incredibly strange thing is that Microsoft clearly put a huge amount of time and effort into making office 2013 look better with fancy animations, etc. And yet the one thing that actually needs to look good - the text - looks dramatically worse for the first time EVER in an office upgrade.
And I can't imagine this is an issue of processor power. I can run office 2010 on my old netbook with great performance. In fact, I can even run office 2010 with an alternative font renderer (mactype) and it STILL performs fantastically well!
Even if it was some obscure registry setting, or even a crazy series of commands in the command line, I wouldn't care - I'll go to any length to make the text legible again.
Just give us the OPTION to render using GDI or at least implement RGB sub-pixel rendering using DirectWrite.
I also sit on a university IT committee, and there's no way I'll be recommending office 2013 until this is ironed out. When you annoy the geeks, you often chase away your biggest customers.