Some people pick it up quickly some people never do. Most can do it with practice and patience. There's a 9 year old in Rochester flying demo 3d flights at fun fly's.

The biggest key is a reliable, well set up helicopter that has been flown and trimmed by an experianced flyer. Its down hill after that and gallon or so of fuel.

Nitro ships are more stable and easier to see and therefore easier to learn to fly than squirelly little electrics.