Umm... let's put it this way... it's super hard, somewhat relies on luck, requires loads of patience and all your hard work can suddenly go down the drain in a flash ^ ^"
But if you succeed, you can hoard a whole bunch of shines of the Pokemon you're chaining. I usually settle for 4 shinies, 7 if it's good looking or I've had a hard time chaining them. Pachirisu's the easiest one for me.
I admit, it was thanks to this that I managed to trade for event Pokes here, as well as other shinies I couldn't get myself.
So, is it worth it? Depends if you like shinies. Loads of shinies of one same Pokemon. If you just want a certain shiny, go for RNG-ing. Personally, I just started with chaining cause I was annoyed how my brother got a random shiny Electrike in his Ruby while I never found one even though I've played longer... Ironically, my first chained shiny was also Electrike =3=