I'm using Onboard Nvidia GeForce 6150 Video without issue...
Although I do like ATI better(for video quality reasons), I will be switching to them when I get a dedicated video card, Along with an ATI TV tuner card... To use with Vista's Media Center ;)
The onboard video cards are using rudimentary drivers developed and signed by both MS and the manufacturer, thats why people dont have problems with them. However if you have a stand alone solution the drivers that MS have for some reason didnt allow me to put my monitor at its native resolution, so thus I had to go with the drivers directly from nVidia.