I think he has mostly character issues - a bit of a self-obsessed, lazy airhead. If Conte manages to cure him of that, he could turn out to be a very good move for Juve as he is a pretty technically gifted player.
If he was still 20/21 yo, I'd go for him, but at 24 already and not seeming to be getting any better, I'd think twice before getting him on a permanent transfer - loan with an option to buy has never looked this good
I'd still go all in for someone like Afellay or a cheap Malouda, though. If they are not available now, would just wait till winter when things could start moving on the Nani front too (not just Afellay) as opposed to just waste 10 mil, if not more, now just for the sake of buying a player, you guys will most likely be trying to get rid of next year (read Elia, Perotti, etc)