Hey Brian,
For my money, I'd probably skip Mill for now and spend twice as much time on Little Piney -- especially in the summer. The water levels on Mill are better than they have been the last few years, but the trout numbers are still WAAAAAY down. It will be a few years before the population rebounds, assuming we continue to get decent rains to recharge the spring pool.
Little Piney's been fishing pretty well. As the water gets warm and oxygen goes down, the fish are getting pushed downstream. In the blue ribbon section, you'll find good catch rates between Lane Spring and Vida Slab. As the water gets warmer, the Vida Slab area will continue to get better. The white ribbon section (Milldam) has also been fishing well, and it should continue to produce until the hottest part of the year. MDC stocks it every three weeks or so, and there's not a lot of fishing pressure compared to some of our other white ribbon areas.
You know how to read water as well as anyone, so I'd just hit it and do your thing. Right now most of the fish are in the pools, but you can still pull some out of the riffles. The basic rule of thumb is smaller sizes on nymphs and larger sizes on dries, but basically traditional patterns -- PT, Hare's Ear, Adams, BWO, EHC, etc. They're not terribly picky about the pattern, but can be touchy about the approach, cast & presentation. Bring a few brown drake patterns as well, just in case. In the white ribbon area, think attractors -- leaches, buggers, glo-bugs, Y2K's.
If you want some company, let me know when you're up. We've still never had the opportunity to fish together.
Walt Fulps
MissouriTroutHunter.com