I can't say I would recommend renting from the shop on the mountain. Had a few friends that rented bikes when we went up for my bachelor party. One of the rear brakes on the one of the bikes was not working whatsoever. I had the tools to fix it (it was a cable actuated disc) but for something as important as brakes, I was pretty underwhelmed that they could let the bike go out that way.
Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction.
E. F. Schumacher