While messing around just now looking for exploits in the game I discovered something very handy.

Pressing the spacebar will open your inventory instead of having to click the icon. This means that if you pick up an item, press space, and then click, the item will be in your inventory without you having to move your mouse at all, this makes it extremely easy to pick things up in a couple of frames with no accuracy required.

Simply click the item, press space, and click again! :-)

I'm tempted to try another run now that I've found this out because I imagine a lot of time can be saved not having to move the mouse back and forth.