My computer wouldn't power up so i took it to the Best Buy ""geeks""--it was late and best buy was still open. The tech looked at my computer, checked the connections, then concluded that the motherboard was fried. I asked him to check the power supply--he did, I think--and he said that the power supply was fine. I took it somewhere else and found out that the power supply (not the motherboard) needed to be replaced. This fix cost me $40. Best Buy and their geek squad have definitely earned the negative press they've received.
Cons: They'd rather sell you a computer than fix the one you have.