It's written up well "Idaho, the Whitewater State".
I haven't done the west fork but I did the Jarbridge (next drainage over) into the main Bruneau a few years ago. Definietely don't do just the West Fork. Combine it or the Jarbridge with the main Bruneau. That was the best part of the trip. Here's a photo album from that trip.
I highly recommend it. 60 miles of wilderness boating!! Some of the most mind-blowing scenery I have ever seen. The book says the west fork is a notch more difficult than the jarbridge but the whitewater is overall pretty tame down there. It's more about doing a four day self support in an amazing place. Definitely go in spring at peak runoff. There is ALOT of class I-II water that moves along nicely if there is water. Plus the best whitewater comes on the last day in five-mile rapid in the Bruneau. Big, pushy read-and-ran rapids with huge holes during peak runoff.