Our experience has been positive in terms of visitors reaction.
Useage is about what we expected -- we will net about $7000 a year
based on 50% share.  We would do better if the machine was more
reliable.  Expect it to break a lot the first month -- they seem to
need some break-in time.  We have a fairly clear contract with the
vendor and would insist on a written deal that gives you the option to
move it and pull it out if you want. We have an image which is an icon
outside our building, and our name.  We have a new major exhibit
coming this summer and hope to use an image from that in the machine.

The judgment about appropriateness is one which every museum needs to
consider for itself.  Any souvenier item runs the risk of being "too
carny".  We discussed the machine among staff and review the machine
design and penny design before making the commitment.  We came down on
the side of kids like them, it makes money, and it is fairly
non-offensive to most people.  You may come to a different conclusion.

Now how about photo sticker machines?