I downloaded this, but . . . maybe I'm using it wrong, or just an idiot, but it seems pretty user-unfriendly for simple tasks. Like, there's no way to tell it "crop five pixels off the left side of this image" except by using the rectangle selection tool, which I can never get to be precise (and plus the placement of the rules makes it hard to see how many pixels the image is anyway).

If I'm missing something obvious, please tell me! Anyway, thanks for the suggestion.