Midnight Beep has a beta of a forthcoming Mac GTD app; Inbox.
This looks very promising! Khoi Vinh of Subtraction asked for it some days ago:
It surprises me, actually, that no one is working on a proper, Cocoa-authored desktop application that is a fully-fledged, elegant version of kGTD.
“Elegant”. Exactly. I want the apps on my [...]