I impromptu DJed a New Year's house party with my iPad using Algoriddim's djay app. Right as the clock hit midnight I simply put it on a table near the already-in-use iPod setup, connected a few wires to the speakers and my headphones, and away we went. People were staring in wonder, everyone wanted a chance to try scratching on the virtual turn-tables and a dance party immediately started.
There are definitely some limitations to the app like only being able to have one cue point per song and the BPM being off on some songs, but in general I like what I see and am excited for the future of the iPad as a DJ tool. I am also doing research into which app will seamlessly incorporate my iPad into my already existing DJ setup. On second thought, maybe I won't throw it all away...
Features of iPad:
Direct access to iTunes music library
Realistic low-latency turntable interface
Automix mode with automatic transition control (Fade, Backspin, Reverse, Brake, Random)
Live Recording (with built–in organizer for recorded performances)
Seamless AirPlay integration (wirelessly transmit your mix to Apple TV or AirPort Express station)
Pre–Cueing (with optional headphones adapter)
BPM analysis with automatic beat and tempo matching
Full visual waveform with beat–synchronized scrubbing
Mixer, Tempo and EQ controls
Cue Point Trigger
Fully optimized for iOS 4.2 multitasking and background operation