Love it. I'm also in the process of adding display of lists to Nosta (example). Bunch of stuff still broken, but should be fixed soon. Nosta is just for viewing, so having a micro-app like Listr will be a great place to link out to for editing lists.

Also, lists are a mess. Clients seem to abuse them and throw all kinds of things in there (like using an empty list event to track the last time the user has checked their notifications). But seems logical that data sanitation is a key thing clients should handle.