Another point is the Shop GUI. Selling/buying huge amounts of items is very tedious the way it is, since increasing/decreasing the amount needs one click for every single item. So to sell, say, a stack of Apricorns you need to click 63 times until you can sell all of them...
A button to increase/decrease by 10 or to go to max would be nice. Another way would be to make it support the scroll wheel. Or maybe both.