What's the best on-the-go task management software?

Despite attempts to get myself to use Things and OmniFocus, I've always gone back to a hand-maintained Excel document plus writing down physical to-do lists if I'm out running errands.  Maybe it's just inertia, or perhaps the simplicity of just typing tasks into cells made everything else feel cumbersome. 

It looks like OmniFocus has better mobile syncing these days, so perhaps it will be easier to use the second time round.  I just tricked the desktop version into giving me another 14-day trial period. 

I could also go for a web-based solution, which would be nice when I've booted my mac into Windows or Ubuntu.  However, none of the web-based versions had clear support for easy mobile use. 

Any advice?