I had a D&D on my 2002 R1... my god! It was the worst friggin' exhaust! Way ugly loud, and it cost me hp. Replaced it with a high-mount Hindle (which is not so good on the track btw) and haven't looked back. I put a GYT-R exhaust on my 04 R1 and it is the wickedest sounding exhaust I think I have ever heard on a 4 cyclinder 4 stroke. Especially after breaking it in.
My wife also had a D&D on her first bike, a 1995 EX-500. That thing was just plain ridiculous if you can imagine a twin-cylinder with a D&D... But the kids seemed to like it when flames shot out the back...