What are some alternatives?
When comparing Qtractor and Deckadance, you can also consider the following products
Ardour - Record, edit, and mix on Linux, Mac OS X, and Windows.
Mixxx - The most powerful free DJ software in the world.
FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.
Mixmeister - Create custom party mixes, burn CDs, or add special effects to MP3s with this line of DJ software for the novice and pro. Offers free trials and user community.
LMMS - Make music with a free, cross-platform tool
Traktor Pro - Flagship DJ software with four decks and a stunning range of creative features for maximum freedom in DJing.