My wife and I along with another couple had a wonderful dinner at this restaurant recently and loved it.
It is tucked away down another of Bellagio's lovely little alley's and up a few steps to their terrace. So yes the ambience is super.
We had a rezzy so we were seated promptly and started working the menus.
The wine list was nice and we picked an Antinori Bolgheri red wine blend which was reasonably priced and was perfect for our meals.
3 of our group had the sea bass which they loved and I had the Milanese which was huge and wonnnnnnderful.
Ristorante Barchetta is a great restaurant I am happy to recommend to you. Enjoy.