Siri integration is nice but only being able to add to the inbox or any single default list is a hindrance, not to mention the lack of smart-add features. I can say "add cheese hash sign groceries to my remember the milk list" and what I get in my inbox on RTM is "cheese #groceries".

It would be very nice if "#groceries" would be converted to a tag instead of left in plain text, and for that matter would be nice to be able to access my other lists through the supplied caldav interface to directly add tasks to shared lists or others which do not make sensible defaults.