The App that has given me most productivity to date is ImOnTime http://www.expersis.com/.
For MY style it seems to be the best way to organise (although it’s not for all) as it’s an active management system (or should i say re-active ???)
Once your in a mindset that any system is a chore and will require maintenance then the “pop up ” reminders that I.O.T. throw up will be accepted as part of the pay-off

I tried GTD on omifocus for 6 months
I never got anything done

I think GTD is over-rated

I think it starts to crumble once your data swells. Inevitably your entries will grow and it will become harder and harder to constantly order and manage tasks.

Also maybe a creative mind is always changing and adapting by the minute. That’s where the GTD system is too rigid

A good article on the subject(link below) talks about why more creative people may have a problem with GTD….That’s me (too much coming in at once & a need to be totally flexible)…heres the article http://zenhabits.net/2009/04/seven-productivity-tips-for-people-that-hate-gtd/