* I use Conkeror (firefox with emacs keybindings), so the Esc key doesn't work right for the app. Probably some way around that, either with a custom page mode, or whatever.
* I'd want the ability to export my checklists.
* The biggest feature I've not been able to find in a checklist app is a) logging of completion, with b) new every X (day, click, week) checklists from a template. The old one should be logged for reference, but considered closed when a new one is created. That way, your (say) morning list is fresh each day, regardless of the state of yesterday's, without any extra step on your part.
I'm not saying you should add these features, I don't know how well they would fit with what you're trying to do, but that's what I'm looking for.