No other recent Nikon lens has been described in so many conflicting ways. It has been characterized as fast and as slow, as sharp and as soft. As an early owner of the 80-400 my own experiences have echoed both extremes at one time or another. On some occasions I've been truly in awe of the range and quality of this zoom. After all, on a D1/X/H it produces a range of 120mm to 600mm, with a respectable f5.6 at the long end. On other occasions I've cursed the lens as soft, slow, or unusable. I've gone back and forth between carrying it and my 80-200 AF-S in my bag. Recently I decided to try to get to the bottom of all this and figure out what is is that is so perplexing about the lens and reach some conclusions on whether to use it or sell it! At nearly $2000, the lens represents a real investment to any shooter and its high price tag and resulting high expectations are part of what have led to concerns on the part of some reviewers.
From the outset the lens has all the earmarks of an obvious winner. It has a massive range, is smaller than the 80-200 AF-S, is f5.6 or faster, and touts VR capability. It seems in line to replace both the 400mm f5.6 and the 80-200 for many uses. What's not to like? For starters, lens speed. It's no f2.8 and therefore won't provide the "pop" of the 80-200 when used in portrait or wildlife settings. Obviously it also won't perform as well in low light. But what about the VR you ask? Certainly the VR can reduce the effect of hand-holding in many situations, but if you hand-hold correctly, your biggest problem at slow shutter speeds may be subject motion. And no IS or VR system can solve that problem for you--at least not yet. I've found the VR very useful when shooting from a canoe or other boat, which is a must for certain wildlife subjects who are otherwise inaccessible. But I haven't found it nearly as compelling for day to day use.
Perhaps the biggest controversy over the 80-400VR is about whether it is sharp or soft. My initial instinct with any pro caliber lens designed by Nikon is to assume it is sharp. After all, they've been making lenses for longer than most of us have been alive and are very good at it. But then I read some reviews that called the 80-400 'soft'. So what's the deal? I was puzzled for quite awhile, as it did seem that I got more than my share of soft images from the 80-400. But clearly if shot correctly the lens can generate tack sharp images. I've shot plenty of those, also. Well, the short story is that it's all about focus. The 80-400 has two major differences from the 80-200 AF-S in the focus department. First, it is slower optically, with a smaller aperture. This gives the camera's AF unit less to work with. As a result the lens hunts more and is slower to acquire focus and quicker to lose focus. The later is truly crucial. You might think that since it is slower to acquire focus it would keep that focus longer. But in my experience it doesn't. If you aren't watching it like a hawk it can easily start to refocus while you are shooting. This is worth repeating: as often as not, at least in my experience, the reason for a soft image is the camera and lens shifting the focus while you're taking the shot. The result is an unsharp or 'soft' shot. It may be correct to cuss out your lens at that point, but it's not the sharpness that is the problem. The problem is that there is not enough contrast in your image to hold the focus steady on the subject. You can correct for this by ensuring that your AF sensor is on a high contrast area or of course by using manual focus. While not quite as easy to manual focus as the M/A mode on the AF-S lenses, the 80-400VR does provide a convenient M<->A selector on the lens which comes in handy at times like this. The second major difference between the 80-200 and 80-400 as far as focusing is the lack of a motor in the 80-400. The 80-200 AF-S (or any AF-S lens) is so quick when focusing that it locks on almost as soon as we zero in on the subject. The 80-400 doesn't do that. It harkens back to the respectable but not lightning fast AF speed of other non-motorized lenses like the 70-300. This would be okay except that we expect it to act like an 80-200, given the price of the lense.
If you're willing to baby the AF issue enough to survive without your 80-200, the smaller size and greater range of the 80-400 is pretty compelling for travel or other space limited situations. It's my #2 lens when I have to pack a light bag (behind my 24-85). But if I have the room & weight allowance, and the time to add and remove Teleconverters, I'd rather be shooting the 80-200 AF-S with (or without) the TC-20E. In particular, for fast changing field sports I find the 80-200 much less frustrating. For flight shots, the 80-400 can be a gem if you pre-focus a little and can anticipate. I spent a morning on an Island with Tufted Puffins hurtling themselves off cliffs and only an 80-400. I was able to capture quite a few good flight shots but I would have been happier if I'd been able to bring along the larger lens and TC. So, for your own use, I suggest you skip over all the comments on Nikon optics--they're probably as good as you need--and cut to the chase on whether the convenience and possibly the VR outweigh the slightly slower and definitely trickier AF. In my case I find the extra inch in my Pro Trekker and the extra range without needing a TC useful enough to take the 80-400VR with me on most trips as the lens on my "over the shoulder" camera while my long lens is on the tripod. --David