I have been waiting for a good DJ app to come to the PlayBook and it looks like there is one making some steady progress. DJPad MP3 DJ by Burnsmod is a nice step in the right direction with a fast interface. From what I can tell the app originated as a WebOS app and also has an Android port. There is definitely quite a bit of improvement to go for the app but the developer Burns Modular is promising updates soon. The most impressive part is that the dev created the app without a PlayBook and is getting one soon to be able to test and clean out the bug.
If you aspire to be a DJ on the side definitely check out DJPad MP3 DJ for $2.99 in App World. You can also check out this free VL-Tone Synth app ported to the PlayBook for some nostalgic fun. Check out a video demo of the WebOS variant below to get an idea of how DJPad works: