Finish construction between terminals and it will be almost perfect.
I've been around quite a few airports in my life and the McCarran has been improved quite a lot from the original. While the original or may be older one was a bit more narrow hallways with slot machines filling them to a greater degree than people the new airport seems brighter with better facilities and much better organization then the older one.
The airport became a hub for America West awhile, which is now part of AA and being a hub it shows. The airport is busy but doesn't feel congested like Newark or JFK. May be for the lack of international traffic but I cannot be sure, but it was a pleasure to fly in and out of this November.