ive done quite a few live shows with my laptop. (software audio console, rme digiface, appsys digital multicore, focusrite/behringer preamps)
bold statement: when u know the band, and have enought time etc. you can compete with the most expensive digital/analogue live mixing desk soundwise (okay, maybe without behringer converters), but if its a chaos gig you will be lost with the mouse, because you are too slow. thats the reason i stopped doing this, although it sounds superior when it works out.
being able to throw a sample to augment the kick and snare is pretty cool at a live gig; and thats just one of the tricks traditional live mixing desks simpy cant do ....