Gmail API
We (Streak, YCS11) have been using this API for a few days to build our email snoozing feature (https://www.streak.com/email-snooze-in-gmail).The API is really nice to use and makes interacting with Gmail way easier relative to IMAP. I'm surprised they don't recommend using this API to build full email clients. I fully expected that to be one of the core use cases.The reason its hard (currently) to build a mail client using the API is that call to list the threads in your inbox or any other label doesn't actually return the messages in those threads. So its hard to show the people that are on the thread as well as some of the timestamp. If they added some more summary data to the thread object, I could see this becoming feasible.