http://www.adorama.com/TM200500NKAF.html#ProductReviews Tamron SP 200-500mm f/5-6.3 Di Auto Focus Zoom Lens with Hood for Nikon AF D There are 5 reviews on the site that all mention sports or wildlife or both as best use of this lens, but I'm just not sure it is fast enough to really make me happy... but for only $800 would it be "good enough"?? Anyone have one of these? Anyone have a strong opinion about shooting 500mm at f6.3? I don't have the money to buy what I really want just now but this really seems like a good deal. opinions?