To me, the best thing about computers for DJing is to be able to locate and load songs very quickly. It was always a pain to sort through those damn Cd's to find the song i wanted. Books that told me where the cd was...having the most used cd's layed out...putting it back in it's proper spot.
I couldn't wait for DJ software to come out. I started bringing a laptop and used it as one of my players. The computer had a 4g HD. So I put the songs on an mp3 cd's and played them off of there. Then I did 2 laptops as players.
like cmwat said, it just takes tasks that a DJ would do and automate them...like any other computer program. I don't believe it makes being a DJ easier. It makes a lot of the tasks a DJ does easier. Many people said that showing people you could DJ with a laptop would kill the industry.