There's a real backlash going on just now with vinyl/cd dj's, against people using mp3's, and encouragingly there's still a lot of young kids buying decks!
And until recently, I have been one of the largest proponents of this backlash. It's not that DJing from your laptop isn't real DJing, it's that public perception could be that whether or not you are mixing yourself, they will assume you're using autosync to mix your tunes anyway. That and of course, MP3's don't sound quite as good as a good old WAV or AIFF file on a CD or the compressionless sound of a vinyl record.
BUT... Unless you're regularly playing in a big club, where you will regularly spin a fairly well defined set for 2 or 3 hours from 100 or so tunes you've handpicked to play (a la the old days when selecting which records to sling in your box for the night), nobody really cares any more! DJ's use laptops everywhere now, 99.9% of the crowd couldn't care less as long as they have a good night. And on most club systems, the only distinguishing factor between a 320kbps MP3 file and a WAV is the bass is slightly muted, so you just turn it up to +2dB on the mixer.
Now the biggest problem, until recently, for me to think about making the move wholesale over to laptop DJing is that for about the last 8 years, pretty much since I stopped buying vinyl, I became Pioneer's biggest fan. I love using CDJ's, I have tried all sorts of other CD decks and digital controllers, and nothing allows me to be as creative or create as smooth a mix as Pioneer CDJ's do, which has kinda nailed the coffin shit on laptop DJing for me... Until now! My mate just bought one of those Pioneer DDJ-T1's the other week, and I had a brief go on it the other night... WOW! Honestly, I'm thinking of selling all my other gear and getting one, it's wonderful! For DJing pretty much anywhere it makes sooooo much sense, and if I did get a gig in a big club again, as I'd know what kind of tunes I'd be playing, I could just turn up with a small CD wallet and use their Pioneer CDJ's anyway as I would have done before.
Though if I had the money, it would be a brace of CDJ2000's connected together, and just use my laptop as the music storage device in conjunction with them. But they are £1500 a piece! 
rob
