Almost perfect...

Very smooth todo+calendar that syncs well to gmail/iCloud/iCal. However, some important features are missing: you cannot tag events synced to app, and you cannot track the time used for any tag or project.
Most importantly, notifications are weak. Natively, It only has 1 alarm. Email/SMS/etc are offloaded to todooledo.
Task list is also non-intuitive for non-GTD people.

Oni_kin about ActionAgenda