Like many other reviewers, I decided to use their airport shuttle service. About $12 gets you round trip service to and from all strip hotels, a good deal considering most taxis around about $30 one way.
My ride to the strip was decent; the van was clean, the driver knew how to drive and helped me with my bags. All was well.
I scheduled my return trip and the van arrived on-time.
Bottom line: Although everything worked out smoothly, I'd advise you just buy a one way ticket. You're better having the flexibility of taking another shuttle service that is already outside of your hotel then scheduling a return trip and hoping it shows up on-time (or at all).