saving as .rtf has a few benifits, as far as I know it can't carry and macro virus (I know virus is a windows thing) some corporate mail systems are starting to filter Word documents due to their ability to do bad things once they are behind the corp firewall
I've some oddities going between Pages and Word. I think a Pages template document looked a little mangled in Word (I can't remember specifically why). My main point of reference, however, was opening a Word document (created in Word:mac 2004) with tables that contained images in the cells (screenshots). When the document was opened in Pages the table cells were all very short and it turned out that the problem was that Pages was treating the images as backgrounds in the cell rather than as block object that it should size itself to.
In answer to the question, yes, you can export Pages documents in .doc format but don't be surprised if it doesn't look 100% correct.