I'd rather ride 99% of my miles on knobby tires on the street, than even 1% of those tires (the ones on it now) on ANY dirt. Actually, I'd rather not ride on the dirt at all with those tires. Ask Aracheon how much he loves the tires on his DRZ. He ended up in a similar situation as you, and fell like 15 times on his first day out. Get some knobbies on that baby. Performance Cycle had a sick deal on dirt tires about a month ago and I picked up a pair of Dunlops for $90. But then again, if you don't have another bike, then having a middle of the road tire might be best for you.
And yeah, heavy ass bike. I love my WR250... light, easy to pick up, easy to flick around.
Otherwise, congrats. I've found a new love for the dirt, and I have a feeling my street bike is going to be jealous next summer.