On the contrary, dell are vey very good compared to similar sized rivals (hp, packard bell, acer etc...) especially online support, you type in the service tag and you can find out EXCActly what is in your machine and the drivers for it. Do that with other brands and you get several possible options.
In my experience, so does Dell -- I've run into quite a few cases where I was presented with three different graphical drivers, 4 sound card drivers and 2 network drivers to pick from after entering the servicetag. Still trial-and-error at times.
But their on-site support and replacement deals are great -- as long as you're willing to pay for the warranty stuff, there are very few problems. It's just that the average home user tends to skip out on 'paying extra' for the higher level of service, and ends up taking a gamble.