I have been to Gio's a number of times, and can say without any hesitation that I have never been (even momentarily) disappointed. The wine, food, atmosphere and service are all consistently excellent. It is, quite possibly, my favorite (affordable) restaurant in all of Toronto.
Housed in an old bank building, the space is large with high ceilings. At night, the lights are lowered and candles lit everywhere, bringing a golden intimacy to the space. For larger parties (of probably 8+), you can even reserve the old bank vault at the back of the restaurant (which has been converted into their wine cellar). It's pretty fun to sit in your own vault surrounded by amazing Italian wines.
Must haves:
Antipasti - grilled calamari with capers and tomatoes (it makes people blush, it is so damn tender!)
Primi - crespelle with butternut squash and sage butter sauce (forget everything else you've ever eaten. This is it right here.)
Secondi (Pesce/Carne) - the whole grilled sea bass is incredible. The involtini and the osso buco are equally amazing.
Always ask your server about the specials as well. They often feature decadent Secondi courses for genuinely reasonable prices.