For the most part, I work at the desk. Sometimes I will take my computer to the bed if the hotel has wireless and/or if it is more convenient to plug the computer into a power outlet by my bed, rather than by the desk.

I have been fortunate in that most of my stays have been at hotels where it is possible to watch the TV and work at the desk at the same time. Some hotels have a cylindrical cushion which is a good back support if you are working in bed.