My experience with hand-holding 200mm in 4/3" format (FOV like 400mm in 35mm format) is that the VF image can bobble around quite a lot. I have had fairly good success getting sharp hand-held images at low shutter speeds with more normal focal lengths is fairly steady, but those bobbling VF images have shattered my hubris, and make me desire "VF image stability".
Thanks for the personal info. I stand corrected. Good to know this from your experience rather than my guess.
I finished some shots tonight to test what I thought was the IS being unstable, thinking it may have been due to operating well below it's intended temp range (-20C tonight, -10 the first time I suspected it). There is a clear difference in the full frame printed at 8x10. Looking at details, the IS was drifting vertically.
There was a comment earlier in this discussion that the IS in some lenses (or Canon in particular was being referred to) hunts when on a tripod. Is there more information on this somewhere? It didn't pop up in a google search.
The lens I used as the Canon EFS 17-85 IS.
It's interesting, but IS may require a certain minimum of shake to avoid creating movement on it's own!
There's a slightly outdated piece of information on Canon USA's website.
The EF-S 17-55mm f/2.8 IS has tripod detection, as does the older EF 70-200mm f/2.8L IS.
As far as I know, all L-class IS lenses after the 70-200 include this tripod detection, but the EF-S 17-85 and EF 100-400mm f/4-5.6L IS do not.