It was definitely hand. Wasn't deliberate hand, but his hand did change the balls direction taking it away from Buffon's dive. The goal could have been given and at the same time it could be disallowed. Its the grey area decision.
Next goal wins this. Juve score, Barca will fold. Barca score, no way back for Juve. Do think someone will score another though.
I remember andy Johnson scoring one like that for everton against Sunderland some years ago, and they said on MoTD is was a legitimate goal as it was unintentional. Then there was Suarez's in the FA cup too.