I rented a travel trailer from RV rental outlet in Mesa two weekends ago. They had the best reviews of the renters in town with TTs. All of the units seems to be fairly new and cosmetically taken care of. It was mostly a positive experience and I would rent from them again.
Its like renting a car and a house at the same time, so a couple of things to be aware of:
Make sure all existing problems are documented and make sure everything works in all modes. I discovered a dead house battery once I got the trailer home and unplugged it from the truck.
At least for the trailer, you are responsible for the tires and whatever damage they cause. i didn't feel comfortable with their unknown mileage/quality/condition tires so I bought their insurance. Like a rental car, they sell insurance for everything which drives the price up.
Hope this helps, it was my first time and was a great way to figure out if I liked it without dropping big $$ on owning.