In DOTA 2, we have the option to use quickcast on key down, quickcast on key release, and normal cast. In addition, we can merge normal cast and quickcast, according to the spell or item we want to use, but players can't use quickcast on key down and quickcast on key release at the same time.
It would be very nice to have quickcast on key down and quickcast on key release simultaneously, according to which skill we are using, since the first is very good for fast reactions, like dodging projectiles with blink dagger and using scythe of vyse on enemies to disable them as fast as possible, and the is second most useful for AOE spells, like chronosfere and sleight of fist, whereas you almost always want to have the perfect notion if it will hit the desired targets or not, but still want to do this as quick as possible.
We already have the option to use normal cast and quickcast at the same time, adding the option to use both types of quickcast at the same time according to the spells or items we want to use will make DOTA 2 more customizable for each player's preferences and more friendly to people that comes from another MOBA that have this implemented.
Thanks in advance and sorry for my bad english.