Has anyone done a comparison on how well the kerning/hyphenation/etc. compare to TeX's? As I understand it, even some commercial packages that are designed for this sort of thing still fail to match TeX's. I could be wrong there, however.
Also, the component that powers Word's text layout also does it for IE7/IE8/IE9, WPF and Silverlight (and maybe more, I don't know).
I've heard that Word doesn't play as well with the text layout component as the component authors would prefer. It's possible that this will improve in the future.
As for TeX vs Word, that's a great question. I know that the authors of Word's text layout engine are familiar with Knuth's dead-tree works on typography, but beyond that, I don't know.
It would be great if someone out there did a blind test of Word vs LaTeX layout. It doesn't seem like it would be that difficult -- just get a few pages of text from Gutenberg and render it in both Word and LaTeX.