It's a gated feed so it will let balls in, but not out.
So it eliminates the need to open and close your lid. Just grab your pot, pop it open, pour in your paint and keep playing.
But be warned...if you get used to it too much you risk making a fool of yourself when using your backup hopper, as this lovely chap did
http://video.google.co.uk/videoplay?docid=-4542406490980265601&hl=en-GB