Daniel pointed out the Image Optimizer ImageOptim to me yesterday and it appears to work magical wonders on transparent PNG's - a filesize reduction of 35% - 44%. Turns out there are plenty of tools out there that do this exact same thing, I've just been ignorant to their existence. Sites like PunyPNG even do it for you online.

Am I a total maroon for not having known about these? Do most developers out there take advantage of these additional compressions?