Actually, the best way to do about smartcasting is 'selective smartcast'. That is, using QWER as regular cast, then shift + QWER when you want to combo someone (or switch them around). This way you get the best of both worlds: have the precision of the targeting reticle when you need to land a crucial spell, and the speed of chain casting/rapid casting when things get hectic.
(People actually underestimate the accuracy of the targeting reticle, because when you shoot a skillshot, your pointer is where your projectile's shadow will pass through, and NOT the projectile itself. Which means if you're shooting straight up/down its ok, but any sort of horizontal and you have this 'fudge factor' that is very to hard to account for when you smartcast.)
As for myself, I used to do this when I was tryharding in ranked and such, but now I smartcast everything just because I'm too lazy to click.
