I hiked about 45 minutes downstream from Devil's hole yesterday. Had a great day. I caught 14 fish--all of them more than 12 inches; I caught one rainbow in a pool that was 18 inches--and fat (to be fair, some of those I caught looked like torpedoes--not an ounce of fat on them). The weather was warmer, which helped to make the fish active. I also saw three beavers (they swam right by me on the creek). I had no idea there were beavers down there. I've never seen any dams or lodges, but these guys looked fat and happy, so there must be enough food for them.
By the way, I go in from Arrowhead, down Hook Creek Road, and drive to Devil's Hole from there. The last bit is rough, but parking at the trailhead isn't too bad.