With the risk of sounding fanboy, this is really fantastic! This could actually be a viable, secure answer to mail encryption.
And this is aawesome too: "we have specifically expanded the scope of our Vulnerability Rewards Program to include End-To-End. This means that reports of exploitable security bugs within End-To-End are eligible for a reward."
This seems like a fantastic idea. We currently use Syncdocs [1] to encrypt our Google Drive folders. It is also end-to-end encryption, but it uses AES, not PGP, which means the key exchange is separate.
If the email is drafted online, do the drafts get deleted and wiped after encryption on the Gmail server?
And this is aawesome too: "we have specifically expanded the scope of our Vulnerability Rewards Program to include End-To-End. This means that reports of exploitable security bugs within End-To-End are eligible for a reward."