I have just turned over 1200 miles on my new 2013, during the first 300 miles, about 100 miles was off road on rutted fire roads / logging trails / mining roads in eastern Tennessee. It performed much better than I had expected, however I did notice extreme hesitation in Enduro mode when I need to "crack the throttle" for slight obstacles.
Others have mentioned "Get a real dirt bike" which I have to say is good advice. I have been riding for well over 45 years now with my first 15 years in the dirt on anything I could get my hands on, as I remember my first "Real Motorcycle" upgrading from my 5hp Rupp mini was a '68 Honda C110 50cc road bike that I quickly modified with knobbies and homemade exhaust and I was giving the Hodaka Super rat's a run for their money!
I have mentored many new riders and my suggestion was always to start with an enduro and graduate to a street bike. The skills learned in the dirt and loose gravel with save your hide on the street when you encounter unexpected variables like sand / gravel on the road. My bike of choice back in the 70's / 80's were Yamaha 650 twins, and I have logged thousand's of miles on the road and often off the beaten path, the love affair with these old thumpers never died, I still have a couple.
I was a "Motor Officer" in Dayton for several years in the late 70's early 80's and believe me, I took a '68 Electra Glide places it should never have gone, sorta like the Bumble Bee, they don't know it is physically impossible to fly, they do it anyway. I remember one instance when I was chasing a stolen dirt bike (KX 250) and ended up on the bikeway along the river, the kid on the stolen bike was in so much shock that I followed him up and over the river levee on a 900+ lb Harley that as he was looking over his shoulder he failed to see the cable across a park road..... end of that chase!
If you are willing to risk broken parts (Bike and self) the Multi will take you places you have never dreamed of, just be willing to "Power On" when needed and don't back off! But first learn both your own personal limitations and the bikes. Your personal limitations will be easier and cheaper learned on a very inexpensive dirt bike or enduro. The bikes limitations are best learned from others with experience and eventually your own. Get with a group of "Dual Sport" riders and get some saddle time, many offer rides that separate riders in ability and bike types.
On another thread we have been discussing putting together a true "Multi Event" that will include a Road trip, Track Day, and a day in the dirt. And I can't think of another motorcycle that would be more capable to do this on than a MTS!