So, far so good. They've been very responsive (every time I wanted a new Perl module added, etc). The only problem I am having at the moment is getting Django working (as they don't support mod_python).
Consequently, I've abandoned my implementation of GTD and started to use Tracks which is a Ruby on Rails implementation. I don't know Ruby (and I don't really have time to learn it), but Rails is well supported by A2 Hosting.