sbolton:
I asked because..........
I also have Outlook 2007 at work, in a Windows environment, but I no longer use it for anything other than company e-mail messages.
For all GTD stuff, I now use Omnifocus on an iPad (waiting for the iPad-specific version) which is always synced with an iTouch via the clouds, using Mobileme. You could do the same with an iPad and your existing iPhone.
I am no longer "stuck" with Outlook 2007 for GTD functions. Omnifocus is head and shoulders better for GTD, particularly if you want to alternately view NA's by Context or by Project, or if you want an "In Box" function that works just like the GTD workflow diagram, or if you want to organize projects by categories.
Another option for your consideration.
rdgeorge