This airport requires a tram ride between ticketing/baggage claim and the terminals. I hate tram rides in airports. Most of the time I'd just rather walk.
Also, the rental car center is a shuttle ride away. I realize this is becoming more and more common with the bigger airports, but I don't like paying all of the "airport recovery fees" on my car rental and still having to take a shuttle bus to get the car!
The passenger pickup area is also really confusing and McCarran is always packed and seems difficult to navigate.
Bonus points for the slot machines, though!