My dd collects them. She loves the disney ones of course, but wherever we go, if there is a machine, she's there!!
We have filled up two of the penny press books we got in Disney and they are just about all filled up. Every once in awhile she will give up more $ and get a pressed quarter.
It's great fun hunting down the machines, pick what we don't have (they usually have at least 2-3 choices, we only let her get one, that way when we go back each year she adds to her collection). I think it's great souveniers. She has a couple of doubles, so if anyone wants to trade, let me know!