Like Kenneth, I think many of the Word "features" Francis cites are mixed blessings, at best. In particular, this claim...
> Word can do search and replace for formatting, special characters and so on. Frame supports a lot of search options but can only replace with text, character format or "by pasting".
...misses the fact that Frame can copy a very useful batch of things, including not just text and tables and objects, but also paragraph or character formatting, table column widths (!), and (most powerfully) conditional text settings. Combine the vast array of things Frame can search for with this diversity of copiable items, and the ability to replace "by pasting" starts to look like an extraordinarily powerful tool. Yeah, it's easier to search for certain special characters in Word, but overall, Frame's Find/Change function gives me power Word can't match. Just try, for instance, using Word to maintain content-sensitive restrictive markings during development of a complex document. If every page that contains a reference to "lefthanded frammistat" needs to be marked "Competition Sensitive" AND every paragraph that contains a frammistat reference needs to be marked with a leading "(CS)" AND your legal department insists that every in-process review draft be correctly marked, how would you approach that using Word? With Frame's combination of conditional text, variables, and the ability to replace-by-pasting styles and conditions, it's easy (I just finished such a project).
I think Thomas' example points to the real difference: Word's interface and features (esp. ones like Autocorrect) make it easier for relatively untrained people to do relatively simple tasks... which makes it a great tool for everyday productivity tasks. For highly trained professionals doing more complex tasks, these productivity features can become more of a hindrance than a help, and the greater power and control afforded by Frame becomes dispositive.
Which may be why even Microsoft doesn't use Word for jobs better suited to Frame.
(PS: Lest you think I'm just a hater, I'll mention that I've been using -- and loving -- Word ever since its initial version... for the Mac... years before Windows even existed.)