I've ridden on it bunch of times as I live in Salida. I've got a WR450F and WR250F, both street legal. The rainbow can be like threading a needle in places, a narrow trail on a steep slope. Parts of it are really nice for riding. But on the Rainbow, I've run into hostile tree hugger types that stopped me and bitched. I ride mostly old mining roads. The Whale Mtn and Bonanza area are excellent riding areas. I'll ride from home to Coaldale, over Hayden pass, through Villa Grove to Bonanza and back to Salida via the old Otto Mears toll road. Been over Marshall Pass and ridden in the Tomichi valley. Also ride in the moquitoe range, Four Mile area. Wellsville area and the power line road early and late season when there's snow higher up. At Texas Creek there's a nice area to ride but I haven't been to it yet. Maybe today.
Staring at it won't fix it. Beer won't either but sometimes the can is useful.