Science and Nature won't accept submissions in Word 2007.

I haven't submitted a paper to Science or Nature recently, but neither journal is accepting submissions in Word 2007 format. It turns out that Word 2007 isn't compatible with their systems, especially equations and Greek letters. This blog has a nice explanation of the situation, with references.

Should you switch to Word 2007? Probably not yet. If Science and Nature aren't ready for it, then the colleague that you send a draft to won't be either. It looks like a .pdf may still be the most universal format for a while.