How about Marché Bacchus? As a tourist visiting the Strip, I didn't think it was worth the drive. However, if I lived in the area, I'd think it was well worth it. It serves simple food, and is one part wine store as well. Buy wine at the store, and there's only a small surcharge to open it while dining at the restaurant.
Summerlin is pretty vast - what part? Grimaldi's (in Boca Park) has good NY-style pizza, on a par with Broadway Pizza on Rancho. There is a terrific taco/burrito/menudo place (Tacos el something, I can't remember the name) in the Albertson's shopping center on Cheyenne and Rampart/Durango (it's next to Steiner's). I second the Vintner Grill and Marche Bacchus recommendations as well. And, if you are in the mood for a good steak but don't feel like going to one of the gazillion Strip steakhouses, the ones at Red Rock Casino (TBones) and Suncoast (SC Prime) are quite good.
10100 W. Charleston Blvd., Las Vegas, NV 89135
2620 Regatta Drive, Las Vegas, NV 89128
Red Rock Bar
1729 E Charleston Blvd Ste A, Las Vegas, NV 89104