it depends on the place and the operator. I would like to think that you shouldn't have to worry about "hurting someone's feelings" in telling them about issues with the games that they have on route. a good operator will take the comment as constructive criticism and address the issue.
operators that don't care or those that give you grief for pointing out issues shouldn't be in the business in the first place. they have to remember that if their machines aren't playing well or parts are broken/worn, people won't drop money into them. additionally, those people will tell their friends (and other nearby customers) to avoid the machines as well.