I have the same view, it doesn't replace riding but it certainly much better then stopping completely and then starting again. It will keep you in shape and prevent you from getting more injuries when you get out cycling again.It is not a good idea, but it is better than not riding. I have used stationary bikes in hotels and such. I usually take my little MP3 player and either use that or plug the earphones into the machine.
At a gym I would spend some time getting a machine set up for me and record the settings. And then use the same machine each day.