Superb. Prices are similar to the Chinatown restaurants, yet the food is better. This restaurant is near Summerlin rather than China town, yet it still attracts many Vietnamese clientele (maybe 50%). Food is quite authentic - surprising so, since the decor is somewhat Western (and quite pleasant). I've traveled in Vietnam, and am always pleased to find the few Vietnamese restaurants in the US that combine both the Vietnamese and French elements of the genre.
I go there at least monthly. Great for business and social. Especially try the beef carpaccio and quail appetizers, curry dishes, grilled beef dishes, catfish, and even the pho is surprisingly good. Healthy food, fresh veggies, good ambiance.
The Vietnamese owners are very helpful and attentive - ask for their recommendations.