I'm 52 and started a year ago. Totally hooked (so to speak) despite slow learnings due to crummy season we're having here. As KIT33R said, wind and weather now dictate my life. The GF said: 'you're too old to be doing this sort of stuff'

Now I'll have to marry her just so I can have the pleasure of a divorce!
Like everyone says: 'good' lessons are a must plus there's a heap of good info on the web. I swatted quite a bit before my first lesson and had a good theoretical handle on the basics and wind window etc before my feet hit the sand. This was invaluable.
Had 3 x 1hr lessons before I fealt confident enough to foist my body dragging self on the unsuspecting public. I wasn't quite up and running but had kite control pretty sorted which is 70% of the story.
Cannot overemphasise the value of the net - I can honestly say that I learned and progressed more from tips on the net than from the 3 hours of lessons. I don't mean to undervalue the need for lessons but it must be said that not once during those three hours were the words 'self rescue' or 'rules of the road' mentioned. And these guys were considered 'reputable'. So in the end, to be comprehensively self-informed wins the day I reckon (same with most things really).
I remember my first decent run and the surprise at how effortless it was. There's a reasonably steep learning curve - thats for sure - but it ain't that hard.
Go for it man.