It works, but I find it's only worth it on skills that are cast in quick succession of each other and jumps. So Zed/Leblanc/Riven I go 100% quick cast. On more mage style champs like Lux/Zyra/Nami I go back to normal cast because I find I have a much higher success rate that way. I take half a second longer to line up the skillshot, or sometimes that extra time allows me to realize I don't need to cast it and hold onto the spell. Taking that time to think(:P not really much time) can be really crucial.
Funnily enough I always play thresh with 100% quick cast, even though the hook is something I'd want to think about, I find that my initial gut instinct is generally more accurate.