The 4 star rating is for the food and service during dinner. It would have been a 5 star meal if the level pretentiousness was dialed down a bit from our server during Happy Hour and the Hostess staff.
We had a 7pm reservation but arrived at 6 for appetizers and a couple of drinks during Happy Hour at Stack. We had the yellow tail, steak and lettuce wraps along with a couple of beers to start off with. The Happy Hour special beer was limited to Bud / Bud Light - we went for Chimay and paid $14/glass - ouch! The appetizers were good, the yellow tail sashimi was fantastic. Great sauce and very good cuts of fish. The steak on the sizzling rocks - good, but I think people may be impressed more by the presentation. The lettuce wraps were also very good - nice blend of flavors. The only downside was that the waitress could have cared less about paying attention to us - she was more concerned with talking with the bartender.
For dinner, we enjoyed items from the $40 Prix Fix menu - probably the best deal we could find. This included an appetizer (all of us had the lobster tacos), a main course (steak, chicken or pasta), and dessert (either the mini doughnuts or the banana bon bon). The food was very good - although the lobster taco appetizer was quite small, the accompanying guacamole sauce was excellent. I had the chicken and grean beans for my main course and it was perfectly done. Juicy and well prepared. Our waiter was attentive, but not overbearing for dinner.
I'd recommend Stack for a very good dinner - and with the set menu that is offered, it's a good deal for Las Vegas dining!