Whatsapp Is Now End-to-End Encrypted

Whatapp is now offering end-to-end message encryption:

Whatsapp will integrate the open-source software Textsecure, created by privacy-focused non-profit Open Whisper Systems, which scrambles messages with a cryptographic key that only the user can access and never leaves his or her device.

I don't know the details, but the article talks about perfect forward secrecy. Moxie Marlinspike is involved, which gives me some confidence that it's a robust implementation.