This shit is gonna cause me to start making mixes again. I love it. It ain't that great for scratching, but I was never a great scratcher. The looping and cue point stuff is at least as good as Final Scratch was back when I was using it around 2005, except it is in one small piece of hardware. Amazing shit.
using the external mixer is a workaround. You do, however, need a separate split cable to cue in your headphones against the master volume. What he did there was to put the cue signal on one side of the external mixer, and the master on the other side, which works out some way that I don't really get.
But it works, apparently.
You can get an official external thing, and there are a couple of options to choose from.
Check for the Numark joints. The pro one is pretty dope, but it costs as much as the damn iPad. Also, apparently the hardware isn't working with iOs 6 yet. But I personally think that an external mixer is a better idea, without having actually tried the setup.
But I've been having plenty of fun with just the ipad.