There’s more to it than meets the eye! Just thought I’d share this gem! 
With best regards,
Steve Mack
Good point.
When I started lessons, I found that I was frustrated at how slow my progress was. I guess I expected that since it was such an easy thing to pick up and make recognizable music from, I could become pretty good, really fast.
Wrong. I owe my teacher, who patiently put up with my impatience, an apology.
It’s like my thinking when I picked up the fiddle at age 40. “Little kids play this thing! How hard can it possibly be?” 
Yep, In The Woods, I agree with that whole-heartedly!
In fact, I think In The Woods, FJohnSharpe, Crookedtune and Cynth are all onto something here! Bolding added for emphasis, of course. But then if it was easy, anyone could do it. One step at a time gets us there eventually!
On the other hand…
Take a look at the “population” of this forum versus flute or uilleann pipes. I think that says something.
I think one can probably get going on the whistle faster than on the flute or pipes, just based on what I’ve read around here, not my own experience. I think a person can get going on the piano more quickly than on the guitar too, and that is based on my experience. But to play well, that would be a whole different thing, at least for me, and I have found no instrument to be easy to play well, that’s for sure.
Whistels are cheap, pipes are really really pricey. I’d love to have a go but I can’t afford one. That’s why I play the whistle.
That’s the beauty of it, laddie. The basics are simple enough so that you can get over the learning curve hump fairly quickly and feel some accomplishment, but the future possibilities are endless.
Well said Brewerpaul
I agree with you, Cynth. All instruments are taken to their absolute limit by the top players, and at that absolute limit they’re all incredibly difficult.