I agree bathroom doors are sensible when traveling with company. When staying alone, though, I prefer no doors. If there is a door, I tend to use a small piece of gaffers' tape to hold it open. I don't spend a lot of time in the hotel room, so while I'm in there I want my movement unimpeded.

The worst I've experienced was a sliding barn door which covered either the bathroom or the clothes rack. If I wanted my clothes to breathe, I had to shut the bathroom with a door that only impedes movement and does not provide privacy. If I wanted to move around freely, I had to shut my clothes in!