No linux support, no firefox support.
Literally the second tweet on their twitter account is 'Damn, it works. Got a lawyer who resisted all other methods to encrypt our comms with @Peerio. Big score for usability. Bravo @kaepora & co.' which kind of bugs me, too.
http://peerio.com/
It's made by the CryptoCat author, so make of that what you will.