Doesn't take long to learn and boy is it worth it.

There have been times when I reverted back a single skill when trying to learn a champion that uses skill shots, such as Lee Sin's Q.

But man.. It's especially worth it if you're using irelia. You will never miss a last hit with her Q and those clutch stuns will really pay off in close top lane engagements.

depends on spells, I try not to put on smartcast spells like blitz or veig stun that need too much acuracy to prevent your enemy from dodging it D:

Cassiopeia's fang. Ryze's... everything. Akali's Q and R. Mostly just on click spells.

I swapped over to Smart Casting thinking it wasn't worth it, I realized quickly the advantages of it.

I highly encourage you to use Smart Casting.

So very worth it, only things I don't use it on is long but limited range ults (ie Lux) or strangely positioned abilities for champs that I don't play much (Veigar stun). It's mandatory on Cassiopeia's E.

Yes, smart casting is amazing. I'd definitely recommend getting used to the combined smart/self cast hotkeys. It makes specific champions feel much.

Edit: better.

Just hold Shift to make any spell smartcast. Then you don't have to bother with switching settings based on the champ you are playing.

YES. Smart casting is amazing. Once you get used to it, you'll feel the difference in how snappy champs feel.

Theres very few characters who dont want it on all of their spells (veigar's stun -- and i can never seem to pull off alistar's headbutt/pound combo w/ smartcast)