Well, the food was generally good. The calamari was disappointing, the tomato soup was tasty and the mushroom pizza was good but too much of something. I loved the first piece but then really struggled to eat any more of it, not sure why. Maybe too much truffle oil made it just too rich?
On the other hand, our waiter was exceptional. He was very friendly and professional and he spent just the right amount of time at the table, never checking on us too often or not often enough.
As a caveat, I absolutely adored this restaurant when it was Stratta. Part of the reason for this trip to Vegas was to eat at Stratta one more time before my husband and I moved to the East Coast. Unfortunately, we didn't do our homework and I didn't know it had changed to Allegro. Once we arrived, I called the Wynn to make reservations at Stratta and they assured me that although the name had changed, the menu was the same. It is not. It has the same structure (i.e. it's a typical Italian menu but it also has a small vegan section) but not the same dishes.
So, 2-stars because I've experienced better both at this "same restaurant" a year ago and elsewhere in Vegas.