I have to agree with much of what Sandy said. The paper I work for is bordered by the Everglades on one side, and the Gulf on the other. Needless to say, lots of wildlife and we do quite a bit of environmental coverage. We're looking into purchasing the 600 along with a 400 and 300 "s" glass. I used the 400/2.8s this weekend to cover a senior PGA golf tournament. First off, the lens is VERY compact and light for a 400/2.8, easily lighter and smaller than the Canon 400 II. Focusing is incredibly fast and of course silent and the lens is very sharp. The background blowout pattern took a bit getting used to however. It's much different from the Canon. I'm not sure which I prefer, but it seems as though the Nikon has more aperture blades giving more of a circular effect. I found it distracting at first. It really blows out the background. I've not had a chance to use the 500s yet, and I haven't seen any weight specs for it either, but I'm willing to bet there isn't much difference. The carbon fiber hood that comes with the S glass doesn't hold up well. The 400 hood is already broken as one of the knobs has fallen off. A great lens though. I also used it with the AF 1.4x on both the 400 and my 80-200. Image quality seemed to drop off with the 80-200 plus the converter. Anyone know whether Nikon makes them based on focal length? Or does one TC work with all? The one stop afforded by the 400 may come in handy in some situations, but generally, longer focal lengths are mandatory for wildlife, especially the shy kind. You'll probably find the 500 too short in many instances. Michel Sandy wrote: >>I wrestled with this decision as well, and finally ended up with the 500 f/4 AF-S. The weight was a consideration (it's difficult enough hauling around the 500 along with other gear!) as was the focal length. I asked for input from the readers of photo.net's nature forum, and the general consensus was to go with the longest lens I could afford for wildlife. Most, including Bob Atkins and Don Baccus who really know their stuff, recommended the 500 as the *shortest* lens to use for wildlife! Another consideration was that I already had the 300 f/4 and TC 14-B, so I had the capability of going to 400mm, albeit at a slower speed. I haven't tried the lens with the TC 14-E, but with the TC 14-B the results are pretty good. Alone, without the TC, the lens is outstanding. The main problem with long lonses is vibration and "heat waves" that can often degrade image quality. Be sure your tripod and ball head can support the weight!<<