I like RememberTheMilk as a to-do list thing. It syncs well with my android phone, which is important. However, there doesn't seem to be a simple option for syncing RTM with my Ubuntu desktop. I currently use Getting Things Gnome! which is OK, but not ideal: syncing has to be done manually (AFAIK) and weirdly, the extra features of GTG are annoying: since RTM doesn't support subtasks, I'd rather not have the option of subtasks on my desktop to-do widget.
I can sync RTM with my google calendar and use that through thunderbird, but this had some weird effects: for every day where I had a to do item with a deadline in the future (i.e. every day) I had an all day event in my calendar for that event: doubleplus suboptimal.
So is there a better option? Preferably one that fits with thunderbird, since that's where all my other organisational shenanigans are taking place.