River Riders was always my choice. They are inexpensive, professional, and fun.
My first trip was the Wenatchee. It was a lot of fun for a first trip. As I recall there was a small section of the Wenatchee that you had to walk around a spillway. Still fun, though.
Personally, my favorite ride was the Methow under good conditions. It's all class 3-4 so the guides will pretty much bust ass through everything.
I have done the Skykomish more than anything because of how close it is. It is a class 5, but that is only one small secction called the Boulder Drop. It's a hoot. If you don't have a strong team in the boat, the guides will walk to raft around the rapid.
River Riders