After a lot of research, I believe the Allen & Heath Xone 2D ($US700) is the best for DJing at the moment (I imagine you don't want to drop 3K on a Xone 3d).
The Vestax VCM-600 looks primo, but it won't be available for a while yet.
At the end of the day it comes down to your own personal technique. Lately I have been running Ableton through an analogue mixer with good results. Though it has it's drawbacks. 1. No buttons to launch clips, 2. The mixing is not recorded as envelopes in Ableton.
The Xone 2D is a good option, as it has a built in 8 channel soundcard with monitoring section. It is also one of the better layed out devices for DJing.
I would use each channel strip as such:
Illuminated button: Cue
The other three buttons: Track Launch, Clip Stop, Track Mute
Fader: Track Volume
The two pots: EQ Low, EQ Mid
Rotary Encoder: Auto Filter (X Axis)
I would use either the jog wheel or the stand-alone rotary encoder for 'scene select'.
And guess what I would use the cross fader for? yep, cross fading.
I think you could do a reaaly tight set with this set up.
http://www.xone.co.uk/2d/