It is a new take on email. I just bumped into them and realised what they are doing is way different than what others are doing.

In my opinion, I would prefer looking at at a more user centric email client like they have.

Not too sure how things would work when there is a group of people talking.

Now that I wrote this, it looks so much like the Messages.app

Looks to me like they're trying to turn email into facebook.