I took my CRF250R out to a motocross track this weekend with my younger brothers. I quickly realized that I am too old for that nonsense...
My cousin (in his mid 40s) races in the 'Vet' class and is amazing on a bike. I don't have much MX experience, and was terrified the whole time that some fast young kid was going to plow into me coming off a jump or something.
I definitely prefer riding open areas and trails. The dunes look like a great time.
The CRF ran awesome. I redid the head two years ago with SS valves and a hi-comp Wiseco piston. But on the last session my brother somehow lost the master link on the chain. I rode my cousin's KX450F which had a Rekluse auto-clutch in it. The bike was too much for me, but that clutch was really sweet. No fear of stalling.