Hi all -
Used a spin dryer last year while staying at a campsite, and to reiterate what Jon said they are usually extremely quiet, in fact I would say almost silent. Also, unlike washers they are designed to be tightly packed, giving little opportunity for the load to whip across to one side of the drum upon startup, and once they hit full speed there should be little, if any, vibration.
On the rare occasion when a load does become unbalanced, it will be apparent as soon as you start the spin dryer up; it will begin to rock somewhat. If this happens, simply redistribute the load, packing it down as firmly as possible, and restart the spin.
Despite being such simple devices I think spin dryers are a lot of fun - it can be interesting to see how much water comes out of a load after it has already been spun in the washer, and feeling how dry the clothes come out has a certain element of "way cool" to it!