A progressively more pressing item on my todo queue is a Libhandy-friendly #Taskwarrior task entry tool. (I've yet to see something on Linux that can match the sleek simplicity of OmniFocus) I'm not super familiar with GTK though... any suggestions for a getting started guide? Same question about a language with good GTK bindings (Vala looks like an interesting learning opportunity, although Python might be more pragmatic).

Not sure from the website, but they fill different roles. My main use for OmniFocus was as a way to quickly file away todos with minimal interruption to whatever task I was currently working on. TaskWarrior comes close, but (a) console only means I need to switch to a terminal to do anything, and (b) (due)date selection was a lot smoother in OmniFocus.