One of the biggest arguments against laptop-based DJ setups is that they just aren't as reliable as a conventional turntable rig. For analog gear, the worst thing you have to worry about is a frayed cable or a warped record--unlike digital DJs who live with a constant fear that a software update may invalidate an audio-card driver or cripple their MIDI controller. The more components in the equation (external storage, USB drivers, software authorization dongles), the more you need a computer science degree just to diagnose the problem.
One way to tackle the reliability is to borrow a page from Apple and make a closed system of software and hardware that is deliberately engineered to work together with a minimum of setup or potential glitches. That's exactly what Vestax has done with its VCI-300 DJ bundle, made in cooperation with the audio software company Serato.
The VCI-300 isn't cheap (around $1,000), but it's not a bad value when you add up the cost of buying a hardware interface, 4-channel audio card, and professional DJ software as separate components. You're still paying a premium for the VCI-300's emphasis on reliability, but it's a small price to pay for some extra peace of mind.
You can read my full review of the Vestax VCI-300 DJ system over on CNET Reviews.