Rented a car back in November 2014, and went without a hitch. I'm not completely certain as to why people are leaving so many negative reviews, but my overall experience was pleasant. I booked a car in advance of arriving, signed up for Hertz Gold and walked straight to the car. Ended up with a Dodge Charger and I honestly can't complain about the car. Did a walk-around to make sure any dents or damages were noted prior to leaving, and ended up returning at the Hertz location inside Caesar's Palace a couple days later. Would definitely rent again from them!
I did note that there was quite a significant line-up at the counter, so maybe the moral of the story is to sign up for Gold in advance so you can walk directly to the car and not have to deal with the counter agents?