I've experienced all three restaurants at Sienna Mercato on numerous occasions, and I am definitely a fan. Emporio (the meatball joint) is a five-star spot for me. The food is so consistently good, they have a great beer selection, a great Happy Hour, and it's pretty affordably priced. They also have Meatball Monday featuring $2 sliders. It's an amazing excuse to go there on a Monday! I really enjoy their rotating Ball of the Month - my favorite was a veal marsala that I believe they had last month.
Mezzo is kind of hit or miss. I've had good meals there, but I've also had risotto that was way underdone (Gordon Ramsay would not be pleased). The service is always good, but quite honestly I would rather eat at the less-bougie meatball level just because every experience I've had there has been so on point!
Il Tetto is a great rooftop bar. I've had a few snacks there - nothing to write home about but better than your standard bar fare. I am always impressed with the beer selection and their cocktails are delicious! This is a great place to take friends from out of town, though it does get busy on weekends.
Overall this is a solid place. Though it's been here for years and other concepts keep popping up nearby, I continue to come back!