Since my backpacking trip to SE Asia, i have been meaning to get myself back into DJing. Just as a hobby. However, the barrier to get going is soo high. You need a mixer or turntables. Speakers etc. Pretty expensive and just a lot of stuff to deal with. Framed in this light i think $19.99 is a cheap price to pay. Of Course there is Traktor, mixer software for your Mac, that works great. However, i find myself to be in the mood to mix at very random times, so having a mixer in my pocket is perfect.
Touch DJ lowered the barrier to entry for my hobby, it got me back into mixing.
The only downside to TouchDJ is that it is not straight forward to add your own music that you want to mix to the app.
The app has no access to your onboard iPhone library. It has to create a separate library for TouchDJ, which can result in inefficient use of memory. Also its simply just not as easy to use.
On their website they recommended that you use the companion Mac app, which i downloaded. I couldn't figure out how to make it useful.
But i did discover a nifty feature that i liked as a better alternative. In the settings menu of Touch DJ there is a button called, "Start Server", simply hit this button and type in the IP address that the app gives you into your web browser on your laptop. This turns TouchDJ into a server on your local wi-fi network, and lets you open a website with a dead simple upload interface for adding mp3 tracks.
Lastly, the app pioneers a cool new interface (at least new to me) for mixing, dubbed Visual Mixing. It creates Peak Files (this takes a long time the first time you do it, but is smooth thereon after) which are sound wave representations of the track. The idea is that you can learn to visually beat match the tracks based on their sound wave peaks.