Hugh Pile wrote:

My workflow is Devonthink
Pro>Curio>Scrivener>MSWord. I also use Yojimbo for simpler storage. I may drop
DevonThink if I find Scrivener or Curio can contain all my research, and I'm actively
looking for a replacement for Word, like Mellel, Nisus Writer Pro or possibly Bean.
But unfortunately no one has so far replicated Word's change-tracking function.

Ha! Never say "no one".

Apple's Pages, contained within iWork 2008 just launched, has a pretty-looking change-tracking function. Pages can even import MS Word's tracked changes, as well as many other Word elements. http://www.apple.com/iwork/pages/

It's still the only such alternative I know of. But a Word-free future has just opened up, should one want it.