I-Naba is one of my favorites places to go for soba (buckwheat) noodles. Last time I went I got the hot soba noodles with mushrooms, spinach, and other vegetables, along with a yam paste which helps with the consistency of the noodle. The service is fast and the restaurant is clean and quaint.
They play pleasant instrumental oldies music (Beatles, etc.) which I appreciate. It is hidden in a mall about 15 minutes from the Strip, but it's worth going.