I really prefer such all-in-one rental car centers over traditional to-each-their-own rental services spread all over. That just means that the shuttle between the airport and the rental center comes very regularly, there is no ambiguity where you need to be (the signs at the airport to get to the shuttle are very clear) and the center itself is convenient and organized.
We had pre-booked with Alamo. We just followed the clear signs at the airport to get to the shuttle. The shuttle driver was courteous and helped with our bags (we had a big car seat bag and stroller in addition to the luggage). The drive is kinda long (the longest drive from airport to rental car that I have seen in the US)-- took almost 12-15 minutes but it gets you very close to the Las Vegas strip itself. The rental car center is clean, organized, air-conditioned (much appreciated in September Nevada heat) and convenient (clean restrooms, enough seating around, easy elevators / escalators up and down and slot machines- if you care for some entertainment right there). We found the queues pretty quick (coming in and going out). In and out in a jiffy-- makes a mom of a tired toddler very happy.