I am letting my 50D go. It served well and I had a lot of fun with it. I will miss my 50D.
The Auto Focus on 7D is very good. With its 8fps continuous shooting ability it serves different purpose than the full-frame brother 5D Mark II. They really complement each other. I'm not much into sports photography but I do love surfing so maybe I'll go down to the beach and shoot some surfers.