I have been using djay to mix in a single iOS device (iPad) and last weekend I did it using two iPads + mixer, which is great for cue, EQ, real stereo image, etc. and looks awesome!
Now the only things I missed were being able to sync tempo on both devices easily or automatically. This could be managed by searching for djay devices on the same Wi-Fi (ie. using Bonjour) or bluetooth network, or at least entering BPM tempo number manually, because sometimes it was very hard to get a specific tempo (ie. 128.0) quickly.
The other feature I missed was checking played tracks on both devices playlists as well (or three or more), to avoid double checking.
I’m sure adding those will make djay even better.