I have tried 11 different GTD apps for my MacBook Pro ... the only one that works down in the trenches for my needs was (gasp) a Windows app (that I run via Parallels Workstation) - MyLifeOrganized (MLO).

I was running kGTD (and really liked it) prior to this [it just was "almost" stable/good enough and it was the "almost" that caused me to leave it as a trusted system].

Anway, MLO has a million features that make it excellent (the interface could sure use some work though). Such as - rapid entry inbox, ability to hide an outline branch in the to-do list (this is really a next action list), designation of task(s) as Projects, assignment of a task as a weekly/monthly/yearly goals (I use mainly the weekly goals feature because it elevates tasks in the next action view), ability to load templates (various built-in GTD templates that were quite helpful), ability to zoom-in ("hoist") on only designated sections, and many excellent Views. There are many, many other features that make it great so please take a look at it.

I would certainly rather work in a native Mac app and I have a feeling (based on my interaction with your other products) that OmniFocus will be it. So good luck with everything!