Hotels not giving you what you ask for/have paid for even though the room you want is available. For example if you ask for a king size bed they'll try to put you in a twin or ask for a quiet room and you find you're between the lift and the ice machine.
For a female perspective, the lack of good lighting in the vicinity of a mirror for putting on make up is frustrating. Also, in UK hotels, electric sockets are not allowed in bathrooms so I end up crouching on the floor with the hair dryer as it's the only place I can plug it in. (Even more frustrating - when the hair dryer flex is half the distance between the socket & the mirror...)