Hide the detector. Stick with traffic. VA is bad but MD is worse. Watch for unmarked Chargers and Mustangs around Baltimore.
You'll likely hit lots of rain from Gustav. I grew up in Philly metro traffic, but Norther Virginians (no offense to natives) struggle with driving in general, and in foul weather, it's a crap shoot...snow is downright comical.
They tail WAY too close, don't pay attention, cut you off, and can't handle their huge vehicles. I can't emphasize enough to increase following distance. Drivers will insist you speed up to close the gap, cut in front of you, or even flick you off, but just stay back. That practice has saved me from getting rear ended countless times. Your 1er can stop MUCH quicker than most vehicles on the road, the guy behind you, leaving no more than 5 feet will inevitably run up your ass if you're forced to stop quickly.
Safe travels, enjoy the trip.