Another capability I really like about iGTD, and am hoping is also within reach with OF, is the ability to use email as a collector. You can send yourself an email (i.e. from a blackberry) and it's automatically put into your iGTD Inbox (and deleted from your Mail inbox).
It's described here:
http://bargiel.home.pl/iGTD/help/usi...ule/index.html