Have done it, some are fine with it some not so much. I did it at one hotel as I had a dog with me and the hotel would not allow dogs. The front desk person was not happy but I moved my TCer to the back of the lot and nothing was said. At another I was told that I would have to pay for two people in the room as they figured that nobody would want to camp in a TCer when there was a nice hotel room, I think they were also thinking that I was going to come in for the free breakfast. After some discussion they agreed.
In the bigger hotels I stopped asking and just did it, in the smaller ones I would tell them what I was doing and didn't ask for permission. The worst part was when the staff started showing up for work and they all want to see this camper in the lot, once they saw it most agree with my desire for my own place and are shocked at how nice it is.
I have not tried it with the class c yet.