Unlike BLT Steak, the prices here don't require an expense account, but the food is in no way the same caliber. The standouts included the garlic bread (served gratis) and a lasagna with meat sauce, which contained sweet pillows of cheese filling enrobed in a rich sauce. But there are some misses too. The chicken parmigiana was thicker than the traditional Italian-American preparation and described by a friend as "chewy". One of our dining companions remarked that some of the dishes were not "piping hot," likely indicating an unduly lag time on the warmer.
The large round tables, with built-in lazy susans, are great for sharing the family-style portions, which worked well with our party of six. One major issue with the dining room is the noise and the lack of any sort of sound absorption. The restaurant--even only 3/4 full--is extremely loud and nearly impossible to hear someone across the large table.
One anomaly--while everything from salads to entrees is meant to be shared, desserts (our tiramisu was delicious) are dainty. While the presentation is creative, the individually-sized portion seemed incongruent to the concept.
The service was attentive, but the up-selling attempts were overly transparent. This is certainly not the best Italian in DC, but by far better than the relatively new DC outpost of the infamous NYC originated Carmine's, of whose atmosphere and food I am highly skeptical of based on a recent happy hour experience, which emphasized quantity over quality.
I would recommend Casa Nonna as a fun option for groups as it provides choices to please pretty much everyone at prices that won't scare those who aren't accustomed to dining out in DC. Casa Nonna also offers a carafe of decent house red wine (reminiscent of Ida's in Boston's North End) for $25, great for sharing. Pastas which serve 2-3 hover around $20 and the shared entrees start at $28.