As a resident of Las Vegas, I've been flying through McCarran for many years - and even more so now, as I travel often for work.
I love that they've expanded the airport and that there are plenty of great food options and shops. Passing through security has never been a problem - knock on wood! Parking is great, if you need it. The passenger pickup areas is small, but you can park a car for a short time, and not be charged. Baggage claim is always quick. There is plenty of space throughout all the terminals.
I've flown through plenty of airports, and McCarran is one of the nicer ones.