According to David Pogue at The New York Times some company did a survey of 20,000 help calls it received, pro-rated for percentage of units in the market, and scored the companies (higher is better):
Lenovo/IBM: 243
Apple: 201
HP/Compaq: 12
Dell: 4
Gateway: 12
Not sure what these scores mean, if anything, but I won’t be buying a Dell anytime soon.