I had my new car delivered yesterday which has the RCD 510 and DAB option.
I've had DAB in my cars for last 3 years and wouldn't be without it (as there are more stations to choose from and reception is better quality than FM and a lot better than MW / LW. Obviously though you need to check what coverage you will have in your area.
VW told me that by having DAB then the multimedia interface (ipod connector) wouldn't work, all I can say is it does
Also got the Dynaudio upgrade so not sure if thats got something to do with it.