I remember seeing a slider concept for adjusting the quantity to grab, that functioned a lot better than trying to use the item icon.
I also saw that little concept but when you have a stack of 500,000 wood that would make it very hard to grab an exact amount, hence my idea. The larger the stack size the harder it is to split it as needed. The keypad, if used with the numpad on your keyboard, could be extremely fast too. Hold shift, click-drag enter 60 on your numpad and hit enter. As long as the game responds fast enough the whole process shouldn't take more than 3 seconds to create a stack. The default #of stacks would always be 1.
Edited:
nah, way too artificial.
i can agree with the whole "shift to grab half" kind of ideas though. it needs to be simplified and made more accurate, but not with a floating keypad.
I guess it could be done without the keypad popping up. You just shift click n drag and then type in a number with your numpad and it subtracts it from the original stack?