One of the fan filters on my Dell laptop got clogged, which caused the graphics chip to overheat (resulting in slow graphics performance and blasting fans). I called Dell in the afternoon on a Monday and did 15 minutes of troubleshooting. They said it might be a problem with the model of graphics card or motherboard.
The next morning there's a Dell tech taking my machine apart, fixing it, and walking out in 20 minutes. Total disruption to my work was less than an hour that week.
Another time I was traveling (for work) in another country and I broke my laptop (dropped it). Dell had a contractor in my office with replacement parts the next day. I didn't have coverage on it though, so that time cost me a few hundred. I'd probably have been SOL with Apple though.