I've been to Mercurio's a couple of times. A decent place for some gourmet pizza and dessert when in Shadyside. The carne e fromaggio appetizer is good; the bread that comes with the meats, cheeses, and arugula plate is nicely toasted without being so crisp that it falls apart. Their pizzas are hit or miss, and light on the toppings in my opinion, but still make for an enjoyable meal.
Off of the pizza menu, I've had the Prosciutto and Pizza Roberto. The Pizza Roberto, in my opinion, is not worth the try (or price)... the home made burrata cheese makes the pizza watery and soggy. Do yourself a favor - save $7 and get the Margherita pizza instead. Luckily I used an online voucher deal during the meal that I ordered the Pizza Roberto, so the disappointment wasn't too damaging.