Christine :
Well, I've shot a fair bit with the 80-400mm VR lens, and it's fine lens for many things. You've asked for strengths and weaknesses to be addressed, so I'll try to oblige.
The 80-400mm VR zoom range is extensive, the VR function works very well, and it's very much a "handholdable" lens for shooting. In terms of versatility, if you have this lens, and maybe the 18-70mm kit lens, you're covered for almost any focal range of interest (unless you need super telephoto distances or extremely wide angle). The VR function really does work neatly, and it compensates to a limited degree for shooting in low light, although the minimum aperture of the lens will have a specific limitation on shutter speeds for a given ISO setting.
The downsides are that the lens isn't AFS, that is, one of the super fast focusing lenses, and that it's not "fast glass", that is, a fairly wide aperture lens (such as an f/2.8). In low light conditions, the 80-400mm is not a great lens for action shooting without higher ISO settings.
Shooting with the 80-400mm lens requires
planning and
anticipation. It's not a lens for a person who wants to machine-gun shoot and let the camera and lens make-up for the photographer's lack of thinking or where the situation simply won't allow for planning the photograph. If a photographer needs a system where they require machine gun shooting, the 80-400mm VR just isn't the lens for them (and they may also want a camera body like the D2Hs - a possible additional expense).
The balance on this is that where I've done some planning, a little thinking about where the bird would fly or how the person will move, I've had good results with the 80-400mm. Even shooting at evening or dawn has been quite possible, and the lens delivered good results. The zoom function and relatively light weight (compared with lenses like the 200-400mm and the 300mm f/2.8) has meant that I could walk around with the lens, and shoot varied subjects and conditions with success.
The 80-400mm lens, IMO, gets a bad rap compared with certain fast primes or with much higher cost zooms. When the lens is considered on its own merits, it's actually a very capable and versatile lens. I'm not the only one to make this comment - no less than Bjørn Rørslett give the lens a high rating (
Bjørn's Take), although he's not happy with the tripod mount (a common comment from Bjørn on many Nikon tele-lenses). In essence, I've found that the 80-400mm lens requires that a photographer learn the specific capabilities of the lens, and work through those for successful shooting.
If you're dead-set on having the "best" wildlife shooting Nikon lens, this may not be the lens for you, although you'll spend roughly four times as much for a lens such as the 200-400mm f/4 VR/AFS, or for a prime like the 300mm f/2.8 and a TC. The 300mm f/4 and a TC are closer to the price of the 80-400mm, but you'll lose the zoom function, and gain only a stop in glass speed, although the AFS function will be much faster.
And those people who claim that the 80-400mm VR lens can't be used for wildlife photography are recommended to look at Janet Zinn's website (
Janet Zinn Photography). Janet's one of the more talented bird photographers around, and she's shot extensively and successfully with the 80-400mm.
So.
The net discussion, IMO, on the 80-400mm VR is that you'd have a very flexible zoom lens with Vibration Reduction that's relatively handholdable at a price point of $1,200-$1,400, which will have some limitations on focus speed and very low light condition shooting. The alternatives in a similar focus length that definitively address those limitations will run substantially more money, and will not, in most cases, be handheld alternatives. There are some intermediate alternatives (e.g., the 70-200mm AFS/VR f/2.8 with TC17EII that you have) that will partially address the issues at hand, at a somewhat increased cost, but will not yield the results of the much more expensive alternatives.
If the focus speed or a "fast glass" (low f/stop) lens are critical deciding factors, the 80-400mm is likely not the lens to choose. If price is a critical factor and you're willing to learn the idiosyncracies of the lens, the 80-400mm VR lens can be an extremely satisfying lens to own.
I hope that this helps.
John P.