encryption, maybe user identification could stand some work....i.e. if google notices the same username being used across multiple devices in multiple locations, take action!!!!
Mail service, the most popular in the world! I like the features about filtering spam and filter mail which private, social, or promoting its good services.
It's really one of the best e-mail clients in the world anyway for all possible reasons out there, it's virus free and so on and on and on really. So hopefully it will be there very very soon anyway. I do not see any obstacles to create few more inboxes.