FWIW, I have never had a good experience with any built-in sound on any computer. Whether they were Creative Labs, Realtek, or some other cheap garbage, the sound quality and drivers were lousy. Until consumers demand better quality en masse, we will continue to be limited to this.
FWIW, HP's laptops with Altec Lansing speakers sound very, very good. They would make a good model for Apple to try to copy if Apple is interested in improving audio quality. I will say as much in the feedback form.