I consider it easier on your knees compared to skiing but hard on your overall body if you fall a lot just learning how to control yourself with a snowboard. it took me about 2-3 years to learn how to carve and switch. and about 4-5 years to do jumps and jibs.
but yes its a lot of fun. i have been doing it for 9 years and i always have withdrawals the day after i have a good session.
My snowboarding career ende the day I tried teaching myself to do it at a park with a pretty good hill ( not mountainous but it looked perfect for a noob snowboarder to learn.) That year it was a way big snow year and I remember going down the hill and almost made it all the way down but then I totally biffed it and my ass landed on a Huge boulder u couldn't see....LOL!