I have changed my gtd system apps a few times now. I have gone from web based to offline apps, Mac only apps to cross plattform and one of the things that always worries me is the vulnerability of the system.
This means what happens if the house is set on fire or the hard drive dies, what if you are on a mac only system and then dont have a mac for some time, what if the app you use ends being developed? These kind of things.

I was wondering what kind of systems you have chosen considering these factors and why.