While my two D50s did ok for baseball and softball, I would sometimes miss a few shots because it wouldn't focus fast enough, mostly running shots. And since I start shooting soccer and football next week,in which the kids are always running, I need faster focusing. I tried my 300f4 (non-AFS) on a D200 body at my local shop last week. focus was definitly faster. So I opted to go this route insted of switching lenses to an AFS version. Besides, I've wanted a D200 anyway. So, I took some of my Smugmug baseball profit, and picked one last week. they had a practice session yesterday at the local MX track. my main purpose was to test focusing speed. I shot a lot of bikes coming at me, at different speeds. I used my 300f4. I'm very happy with the focusing speed now. 1/1000 shutter speed series; 1/200 panning shot; 1/2000 fly-bys If it does this well on MX bikes, I think I'll be able to keep the 6-10 year old kids in focus.