I just went up there for Christmas. I had intended to spend a couple days on the lake and a couple days on the Obey, but the whole trip was pretty much a disaster - way too long of a story to go into here. Anyway, setting aside that long story, I got an hour or two of wading in on Christmas Day and then four hours floating the day after (before the boat broke down - but like I said, long story).
Regardless, I wish I could have fished more, but it was quite good for the time I fished. Near the dam it was mostly dinks, but once I got downriver a couple miles I found some decent rainbows in the 15-17 inch range.
Best results were on the standard midge stuff - thread midges and zebras fished about a foot under an indicator. I'd just cruise along until I found a group of rising fish, and then I'd stop and land the midge in the middle of the rise rings. Sometimes I'd have to sit for a minute or two, but sooner or later one would grab it every time. I tried some streamer stuff but not much results there.
Anyway, the fishing ought to be worth the drive - good luck and let us know how you do.
bd