Godfrey DiGiorgi , Apr 05, 2010; 11:45 a.m.
Personally, I use a tripod for most work at focal lengths beyond 50mm, certainly for 70-100mm and above, although I've hand-held 135-200 mm non-stabilized lenses occasionally.
The Panasonic 45-200 OIS lens is pretty easy to hand-hold at 200mm setting with Mode 1 OIS enabled. Jitter does become troublesome with non-stabilized long lenses.
200mm constitutes 8x normal focal length magnification, so it should be no surprise that it is challenging to hold steadily. The diagonal FoV at 300mm is equivalent to a 600mm lens on 35mm Film format ... that's a very long lens with 12x normal magnification. I never hand-held that long a lens with anything approaching satisfactory results even when I was in my twenties. The upcoming 100-300 OIS lens should make some hand-holdable operation possible.