We spent 3 weeks on our trip in Northern BC, Yukon, and NWT and the rental truck/camper combo's were everywhere. Lots of people would fly into Whitehorse, then rent a set-up and drive north from there. 99% of the ones we saw were new Ford F-350's.
We saw one of the Teton Backcountry Rental's Four Wheel Campers in Yellowstone two weeks ago. The guy had obviously forgotten to do the roof latches as the roof was partially up. I would think that happens frequently with the rentals as I have done it myself more than once. At least with a hard side you won't have that problem.