How effective is the in-camera IS technology from the following manufacturers... when used with lenses of a 200mm focal length and longer?

PENTAX
Olympus
Sony

Would like to hear first-hand experience from people who use IS-equipped camera(s) from the above manufacturers, with lenses of a 200mm focal length or longer. Is the image-stabilizer as effective as with shorter focal-length lenses?

And please mention which camera/lens model you used.