This fork should really be considered the main fork of the Jarbidge. At high flows the run from Murphy Hot Springs is fast and continuous with few eddies and pools. Check it out from the road while driving to put-in for the Jarbidge/Bruneau, and make sure to pay attention for logs/low branches. This is a narrow creek with wood shifting frequently, but is also a nice exhilarating rip with water.
Most of the moves are not harder than class III, but the run doesn't let up for its entirety and some wood/brush hazards keep you on your toes throughout. The final mile picks up gradient, and is a ripping long class 3+ rapid all the way to the forks. The hardest bit can be easily seen from the road, just before the river drops away from it about 1/4 mile above its end. At high flows you might find a nice place wave at the confluence.
At lower flows (typical for this part of the desert), this run is probably a class 3- bump n grind. At any flow its not really worth a drive out on its own, but is cool to check off while putting on/taking off a multi day trip on the downstream Jarbidge/Bruneau. Theres also an abundance of great free camping in the vicinity, and the canyon is a beautiful place to hang out.