Gio would be though can you remember how he played against Chelsea.. he tore John Terry an Ashley cole a new asshole for their hookers to explore.
I wouldn't judge his overall CL pedigree based on that breakout game, as no one (ie Chelsea) had any idea who he was or his attributes. Still, he would be useful in the CL in my opinion because of his style and unpredictability. We'll find the same wall of defenders in these games, so you risk a draw or take a different kind of risk with someone like Giovinco or even Elia.
I remember he did particularly well against Maccabi Haifa and Bordeaux in the home games, which tended to be the ones he was trusted in rather than the away games. He'll still find that that will often be the case when he comes back, but he's becoming a more decisive player.
He won't take all the penalties, freekicks, corners, throw ins and goalkicks if he comes back to Juve, but he'd be a useful weapon to have.