yes, have done it. upgrade depends on funds available and if you are happy to sit in economy for 11 hours. i have been OK with economy on VS, and as im paying for the ticket i want the cheapest available fare.
if you win at the casinos (yeh right) you can always upgrade for the overnight flight back.
i like mccarran, its close to the strip, and the view of the airfield and the hotels on the strip from the departure lounge must be one of the best around.