Nothing really.  Its like itunes, it frees you up to check your email during a show.   

The answer is kind of strange:  "As much skill as the DJ puts into it."

There's a lot of guys -- not famous guys, coincidentally -- that show up with an Ableton setup and use it as a beatmatching shortcut.  They typically don't do well, either creatively or in terms of audience appreciation.

Other guys bring it:  live remixing, improvisation, etc...  They do better.

Respect to deeflash! Make senses to use tracktor when yr djing hiphop as well!

Ableton is an awesome bit of kit and i find i keep learning and trying new things all the time.

Ableton will only do what a dj or performer creativily sets and controls it to do. Carl cox was know for using 3 decks now can use 8 or more.

An example of where the skill is in ableton would be how the dj programs the midi controller! Theres lots of options !

Dave and others with argue that its more like performing than djing. Which is a fair argument. But cheating it aint! Those who say its cheating either don't really understand how ableton works or have never fully had a go with it!

On the other hand i can see why folk might be disapointed (including myself) with Carl Cox using it because he is known for a particular style energy when on the decks. But lets see what he comes up with!

Check ableton.com and the artists section to see what else is possible!

Even with a traditional kit, it's still just sliders and knobs. The crowd doesn't know what you are doing technically and it doesn't care. They want to hear good music and have a good time. In most cases, that also includes finding a member of the opposite sex and some alcohol.

It's more of a case of the argument just doesn't matter. Use the tools that allow you to do your job the best. For some, that's a traditional kit. For others, it's not.

some DJs will sample to crowd during their set and do some live loops of them or others will do live looping of a singer's vocals or something and then use them throughout the set...  Plus with Ableton doing the technical stuff of beatmatching, keeping sync, etc... that frees the DJ to interface with the crowd with eye contact, vocally, etc...  and if the DJ knows his ableton template well (hopefully he'll set it up before his gig  ) he won't need to look at his screen all that much...  once I have a groove going I can use my BCR2000 to control ableton's effects and the trigger finger to select clips and fire them off and it wouldn't even look like I'm using the laptop for much more than when the guys use serato or traktor... 

more creative DJs / performers will throw in some live drum loops they make on the fly, or synth loops they make on the fly using midi controllers etc... 

But yeah, from a strictly DJ standpoint, once you have your setup solid, you just drag and drop the tracks you wanna use, and then you use your controllers to do everything else where you hardly look at the screen... but yeah, it is completely possible to get lost in tweaking, controlling, mixing, etc and lose the contact with crowd, but I don't see how that is much different than with two decks and a mixer...  a lot of guys can keep their eyes on the decks and mixer all night long and not even interface with the crowd once and it's the same issue... 

I agree with Dave, whatever works for the DJ is good with me... if the house rocks w/ Ableton, the house rocks w/ Ableton, if they rock the place with an iTunes playlist, and everyone has a great time they obviously did what they were paid to do... 

I guess that's what I'm curious about... Why do you choose for ableton rather than cds or vinyl? It is just from a practical (not dragging records or cds around, having access to your complete music archive) and financial (mp3s are cheaper) point of view or are there other arguments?

The question would be more like: "Why does ableton allow you to do your job at best?"

I guess it really comes down to, try it... if you like it, great. if not, go back to what you like. :-)