I used it once, in Pokemon Red, my first Pokemon game ever of course... on Articuno lol. I didn't know! I thought he was gonna be the coolest (heh, ice) thing I ever saw! XD
Now I never use it, waaay more fun to catch them 'regularly'. More challenge, more fun to me.
I could understand using it on the ones that run around the world and you gotta chase them/they always run away from you. I maybe did that one time (not in Gold, one of the later ones, White 2 maybe?) but in general I find it just more fun to catch them with normal balls.
Also I'm a hoarder, known to KEEP EVERYTHING FOR A RAINY DAY! You'll never know when you might need it! Don't waste it! So I just never use it. :P