I rented in the Pyrenees and in Maui. In both cases, I would have preferred to have my own bike with me. In France, the Kuota they have me was not comfortable, and did not handle well. In Maui, the Specialized I rented was a great bike, but when I got to the top of the Volcano I was left thinking “this would be so much better if I’d brought MY bike.”
If I went on trips like that on a regular basis, I probably would invest in a good bike bag and either pay the travel fees or try and disguise the bag enough to sneak it through.