we have them in all aircraft.
never used them myself, EVS does have a mock up they will demo for you if you like, plus they will send you DVD and other propaganda.
Buying multiple units does save some money also! (we have 2 in each aircraft)
They take up the room of approx. a Jepp Binder.
they do have a MX schedule, I think its fairly simple.....
I figure, why not?....at the cost of eqiuipment we fly its just a drop in the bucket and may just save you god forbid you need it!!!!!