I've got a 10' WR250R that I dual sport on, about 90% off road. I've modded it out pretty well, have a power commander, etc.
I belong to a group called Great Lakes Dual Sporters, about a 1000 member dual sport club, and ride with a core group of 5-6 guys. I'm the "biggest guy" of the group riding the smallest bike, and I'm always keeping up with the big boys and big toys. Single track, two track, you name it. I love this bike. I ride with a 500 EXC, 2 Beta 300RR's, a Gas Gas 250, and WR450F respectively.
Of the 14 bikes I've had, I think this is probably the best I've owned. It doesn't do anything really well, but does everything "good enough" that it's pretty much the perfect bike for me. I'm sure if I added an Athena big bore kit, I'd probably never buy another bike again unless they made the same model 30lbs lighter. I've briefly considered the Beta XTrainer, but I'm not convinced yet that I need to sell my WRR. :)