Had my 500 out on a back country road which had some pretty new gravel on it...and lots of it. I have ridden for many years with different bikes of all makes and sizes on gravel and i have to say that the MP3 is one of the twitchiest on gravel that I have ever ridden...was not unsafe but still required a great deal of attention. Found that the back end wanted to go in directions that I really had no intention of going. The problem i think is the small diameter wheels. It handles much better at a slower speed...60 Kilometers per hour was about the top speed I could manage safely (about 35-40 MPH). Once off the sections that had an over abundance of gravel and on to a more civilized amount, I was able to do 80-90 KPH without any difficulty whatsoever...so be warned that if you happen to get into deep gravel..keep it slow and a loose grip on the handlebars helps a lot.
Ride safe... :)