I don't have any gauge or level beta - I grew up a few hours away from there, spent two summers at the Boy Scout camp kayaking and rafting, and then managed to get out there a couple times a year for 10+ years, from mid-May to mid August. Since I moved to Colorado 5 years ago I've only been back once - mid June 2009, after exiting the Middle Fork we did the Pine to Panther run. Water was was high, big waves, fun, and coming down from peak run-off flows. I'll be running the stretch from Spring Creek (mile upriver from Shoup) down to Corn Creek in early July this year prior to launching on the Main.
The water on these stretches of the Main is much warmer than the Middle Fork and can get really warm by mid to late summer.
Spring Creek is a good campground but mosquito infested until it gets hot and the swamp areas dry out in mid summer. The developed camp sites in that campground fill up on the weekend but are empty during the week. There is some good open camping up Panther Creek and there are next to no mosquitos there.
There is a hotspring up Panther Creek road that is fun to explore in the evenings.