- A single power socket far from the bed (or worse yet, none at all, so that you have to unplug the kettle, TV etc.)
- Patchy wifi (if you're going to claim to offer it, it has to reach *all* rooms adequately)
What else?
(I should note that it amazes me that many hotels don't seem to have ever "tested" their rooms. If I were a hotel manager, I'd randomly book myself into different rooms every few nights and record & FIX every problem.)