My dad was one, and a good one (poker). My mum has always said "never get involved with a gambler, moreso a good one"... if they can bluff successfully, then they can lie far too well
If they are a bad one, then it is the debt etc to worry about.
If there is a child aspect in the future too, then there is some theory about it being passed on (like alcoholism). I know that I could easily become a gambler (I can see it in my personality), so I just don't do anything like it - like never taking the first drink!