Yep there's DAB boxes from Pioneer and others, but, as it does with digital TV (Sky, Cable and Terrestrial) the quality depends upon how much bandwidth the transmitting channel has bought. Often the end user results can be such that quality seems inferior to FM - no fault of the equipment but all down to stingy radio channel bosses. That's why the uptake is very slow.
Most people now prefer to connect their 60Gb ipod to their car for hours of advert free listening - with the right hardware this can give very good results - much better than DAB.