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A browser extension for Chrome/Chromium is being worked on! You can track it at https://github.com/WhisperSystems/TextSecure-Browser
That's excellent. Installing and using GPG (or GPGTools or GPG Keychain or whatever it's name is) on OS X is awful. Something that's still OSS and cares about UX (like Signal on iOS) would be fantastic.
I don't understand what's so difficult here. The biggest problem is understanding how PGP works, and having to type a password now and then. I use it all the time, to sign - not encrypt - my mail.