PiTouch and HDMIPi Day One
I just got my PiTouch, too. It arrived the same day as my HDMIPi, ironically.
I haven't yet managed to get my HDMIPi working - whatever I do, the screen won't turn on - so I can't do a comparison of screen quality, but in every other aspect the PiTouch wins in direct comparison. It has a capacitive touch screen, it has better build quality, and it works "out of the box" (quite important, in my case ). There are also built-in speakers, a USB hub, two HDMI ports and a composite video input. The enclosure encases the whole device, so I would definitely feel safer using the PiTouch as a portable solution than the HDMIPi which has a relatively "open" enclosure.
So far, I've also used it with my Macbook Pro, a couple of those "Android on a stick" devices, and my phone....but, ironically, not yet with any of my Pis which are tied up in audio based projects ATM. I'll try KivyPie in a bit (thanks for the suggestion, Garth). I need to do a bit of work on the android sticks to get the touchscreen to pick up location (taps are already working) but with every other device it's working perfectly already.
At the moment, because my HDMIPi isn't working, PiTouch is a clear winner. I'm very pleased with my PiTouch purchase, and even if I get the HDMIPi working, I don't think I'll be using it anywhere near as much as my PiTouch - the touch functionality alone swings it for me.
Overall, highly recommended.