My first, last, and hopefully only experience with them was something like this.

I was moving a few states away, so I rented one of the units you tow behind your car, and bought a tow hitch from them. They took care of installing the hitch and hooking up the trailer. First 3/4 of the drive, no problems. Then, suddenly, in the middle of I-5 going 70 mph, the trailer just DETACHES from my car. Thankfully, the safety chains still held and I managed to get it off the road without incident, but I thought for sure that the trailer would hit someone or flip and cause a pileup. What had happened was the pin holding the bigger pin in place on the tow hitch came out, which made the bigger pin wiggle its way out until the whole thing just came off of my car.

Called up U-Haul roadside assistance, and after getting bounced around between a few different people, was told that we could get roadside assistance, but that since it was a problem with a piece of equipment that we bought from them, not rented, that we would have to pay for it all ourselves. It didn't matter that this piece of equipment was installed by one of their employees. Said "screw this", called up AAA, and was told that I couldn't get help 'cause of the U-haul thing, so I had to go crawling back to U-Haul. All in all, it took 3 hours to get off the side of I-5 as evening turned into night, and some random guy actually ended up stopping and happened to have the parts we needed (they looked a lot sturdier than the stuff the U-Haul guy installed). He was remounting the trailer just as the roadside assistance showed up.

It was my first time renting a tow unit and towing something from my car, so even though I have no idea when the first pin came out, I might've caught it if it hadn't happened after a stop I made. From that moment until I made it to my destination, though, you'd better believe I checked that damn hitch every stop I made.

tl;dr - Trailer came unhitched in the middle of I-5 and nearly caused a pileup. 0/10 would not rent from again.