Apart from the long waiting time in line, everything else is 5-star.

The staff persistently tried to upsell without asking.

I purposely rented a large car, but they gave me a different one, claiming it was the same class, which couldn't fit my luggage.

Waited about 90 mintes in line to get to SLC Thrifty agent. Completed all paperwork and had to wait an additional 40 minutes to be told the Suburban rented was not available- check engine light, with no other Suburbans available. Was offered two smaller SUVs to compensate for space, but only had one driver. Had to squeeze into a Chevy Tahoe - 6 passengers total plus luggage. 4 teens sat across the back for their tour of Grand Tenton and Yellowstone. I rented a Suburban due to combination of three rows and combined luggage space. Nothing compares to that vehicle platform.

Booking platform is easy with no issues.

Like: I was three hours early checking in. I was told that car I reserved was not available at that time. Rather than wait, only vehicle available was a Ford Explorer for additional $120. Seemed unusual that you only had this vehicle available for almost 50% more!
Dislike: I think I was "upsold".