Yes, my experience is in the northern end of the park. My daughter worked in the Park's Fly Shop last summer and I was able to use that as excuse to get two fishing trips to YNP.
I learned a lot about fishing the park and I had a lot of fun. Park’s has four full time guides and they have all been with the shop for years. My daughter fished with all of them during the summer. I only fished with Richard, but I met all of the guides and I would happily go back and fish with any of them.
Richard owns the shop and he is a walking encyclopedia about YNP for access points, the seasons to fish the different waters within the park, and even park history. He’s in his 70’s, but it was a challenge to keep up with him. He’s been hiking in the park his whole life. Walter is the shop’s head guide. He’d be my choice for a float trip on the Yellowstone river. Ben seemed to be the most adventuresome of the group and would be my choice if you want the chance to fish waters that very few people will ever see. I would very much like to go back and fish with Ben. Wilson would be the most fun to spend the day with. He’s a nice guy and easy to talk to. Wilson and Ben were extremely helpful to me in August, with fly recommendations, location tips, and access recommendations. They were very generous with information, I liked both of these guys. The shop itself is kind of small and not much to look at, but it maintains one of best and most current fishing reports in the area and they stock a lot of shop tied flies.
Here are the three main points that I learned about fishing YNP:
1. The park water fishes very seasonally and changes throughout the summer season. The rivers and streams that fish best in June will be completely different in August. The thermal features of the park cause some of the waters to warm up too much during the summer and the trout move out of them and into cooler waters.
2. There are no “honey holes”. The fish are everywhere in the right waters (see #1). The number one rule for success in the YNP is to pick a place where nobody else is fishing. There is too much good water available to follow someone else through a spot. There is no reason to fish water that someone else has already fished.
3. The park is very big. You can easily spend several hours in your car trying to move to a fishing spot. If you are hiring a guide, try to pick one that is located close to where you will be fishing. Personally, I’d rather spend more time on the water than in a car when I’m with a guide.
Here are my trip reports from this summer. They pretty much sum up everything I know about the park. http://texasfishingforum.com/forums/ubbthreads.php/topics/10941996/Yellowstone#Post10941996http://texasfishingforum.com/forums/ubbthreads.php/topics/11058111/Yellowstone_Part_2#Post11058111
It is a great place. Have fun!