I don't have experience with the new Battenkill III, but I recently bought a new Battenkill V, the biggest one they make now. I bought it to use as a 7 wt spey reel. It is very well made, with close tolerances. It has a good strong clicker that is internally adjustable. If the III model is made as well as the V, I think it should be fine as a trout reel. You will probably have to palm it to slow down a 20" trout in moving water, but it has a good palming rim.

Regards,
Ted