I've only fished it once, this was back in early spring of last year, but I only caught stocked trout. From what I remember reading old posts, I think it may get too warm in the summer to hold wild trout, but I could be wrong as I'm not too familiar with the area.
I fish this stream often enough and in my experience you will get a few holdovers, but nothing wide spread. As far as wild fish, I saw someone catch a wild brookie once, so perhaps there are more, but that was only one time.
I would agree with the above. Trough Creek is a beautiful piece of water. I think it has been at least 15 years since I fished it and would sure like to get back on it again. Never fished for Smallies on it - but that sounds like a lot of fun.