My Grandfather was an undiagnosed sufferer and passed away at the age of 75, which is when my family found out about it. My father is also a sufferer, however it is completely under control with regular phlebotomies. I Believe it is the most common genetic disorder in caucasians.
I am a carrier, and the old school of thought was that as a carrier you should have no problems with iron levels. However there are now mutterings that this may not be the case, so just to be sure i have my ferritin levels checked every year.
I hold a UK class one medical and have always told the CAA and all AME's that i'm a carrier. Never had any issues.
There is a very good website run by the haemochromatosis society. Not sure about the exact address, but can't be hard to find.
Just one thing about becoming a blood donor though if you are a full sufferer. Different countries have different rules. However my father is not allowed to be a blood donor due to the disorder.