I've flown in and out of PHX a couple of times and I've been pleased with each experience.
The airport has good signage and is easy to navigate through.
The Rental Car Center is located a few minutes away from the airport and there's a free shuttle that takes you to and from the location. If catching the shuttle to the Rental Car Center, the shuttle stops by the curb right outside of the baggage claim area. The shuttle runs continuously and the wait time has virtually been zero for me the times that I've had to use it. It seems to be a very efficiently run operation.
Just an observation, but the airport is a little on the older, more run down looking side. It is also not very spacious so the walkways and seating areas can get crowded.