Thanks!
As you're probably aware, it's good idea to keep the shutter speed at somewhere around or above 1 / focallength when shooting without VR/IS.
So, with the 80-400 that's usually about 1/500 with a bit of a fudge factor. I normally have the VR still on, and usually use
mode 2 (where the VR is on at half button press and previewed in the viewfinder).
With your 70-200 and maybe a 1.4 or 1.7 TC, that's 1/280 or 1/340 at full reach that you'd be looking at unassisted by VR.
In that case at 1/500s, its probably still worthwhile having VR on.
I've only ever turned the the VR off handheld when I'm looking at 1/1000 or faster, primarily only to save battery life. But I find the VR when you've got it in
mode 2 (active), the VR assisted viewfinder helps you line up and steady yourself for the shot anyway when working with longer focal lengths.
Some suggest that the VR can reduce the AF performance. I'm not so sure about this idea, I don't think it makes that much difference... if any.
What I have found with VR/IS, is that my keeper rate is better if I allow the VR to settle before taking the shot where possible.
You'll notice if you're shooting with the VR enabled at half button press (mode 2), that when you first line up the shot and the VR switches on, theres a bit of a noticeable shake going on. Approximately a second later, everything settles down and appears stabilised. Firing off a shot in that period where the VR is still settling can have occasionally unpredictable results.