I don't often bring up my hobby in conversation but I've only ever received positive comments when the word gets out. There's usually the strange expression on their face when they first hear it, but once the thought process goes through they think it's really cool. Generally people hear about it through others like my wife or friends who can't help but tell other people "hey this guy owns a pinball machine!". I don't hide it, but I don't generally bring it up either because, really, I'm not interested in their niche hobby either so figure they aren't that interested in mine.
The funny thing is, at family gathering the guys in my extended family just can't stop talking to me about pinball when they hear I have some or that I play in leagues. It has never ceased to surprise me how many people used to (and still do but didn't know they were still around) play and love pinball and beg me to let them come around and have some games.
Every man has a hobby, for those that don't I feel sorry for them and they are most likely being put in a box by their significant other or parents. I have a father in law that collects cars, I have a brother who collects and has hundreds of power insulators. Men need their toys or they go crazy in my opinion, it's just a matter of how many toys and how much they cost.