I have an '08 with EDC and when I was stationed in England (you can see my GB tag in the picture) I drove the M3 from England through Belgium, France, Germany, Austria, to Rome Italy and back. Man, I miss driving there.
So I tried all three settings. And like most have reported. Normal & Sport mode will either be bumpy & bumpier depending on the road. But the streaches of Autobahn, & Autostrada's that were smooth enough to cruise at 120mph steady speed in "sport" mode I noticed was from Frankfurt to Dunkerk France where I got on/off the ferry to England. From Munich south into Switzerland and from Florence to Rome on the A1. Also from Milan/Monza to/from Verona was the smoothest of the Autostrada's that I kept it in "sport" mode and cruised at 120~140mph.
The switch backs of Monaco were best suited for the "normal" mode IMO.
Now I hardly ever put it in "sport" mode anymore on the shit bumpy and screwed up roads of New Mexico and hardly can ever hit past 100mph for more than 3 seconds for fear of getting arrested. Yeah, I'm not enjoying this M3 like I used to. Can I get another assingment to Europe please?!?!