Yeah, Diablo's tetris-style inventory is very good. Big items look big and occupy bigger space, small items are just the opposite. Right from the start, it adds realism to both item size and space allocation. But I want a hybrid system of tetris and tabbed list (like in DA:O) inventories. According to this, the primary tab is the tetris. The other tabs should be available once you aquire the relevant item container. For instance, when you buy a scroll case, you put it into the tetris and automatically the "SCROLLS" tab opens up and replaces the area of the tetris when opened. You either click the scroll case in the tetris, or the scrolls tab at the top to see the list of scrolls you have in it. It should be the same thing for small items which are expressed by quantity instead of size and weight: Potions, ingredients, rings, amulets etc.
Again, a character should have only one quiver slot and when you click it, it opens a list to show all the arrows you have. When you highlight a type of arrow, you make it the current ammo. You close the list by clicking the quiver.