I've eaten at two places in Aria:

P.U.B. by Todd English - a nice gastro-pub with a good beer selection. The Spotted Pig it isn't, but it's a nice addition to Las Vegas. Very loud. Good for a group of guys out for a night on the town.

Sirio Restorante - all the dishes were lovely, and the charcuterie sampler app was to die for... my aunt, who has traveled in Italy extensively, said it was some of the best prosciutto she's had in her life. Waiter was very attentive and helpful.