Recently purchased a nikon 300mm 2.8 for use on a D3x. With the relatively low noise the camera produces, I find that I can just dial up the ASA and get useable shutter speeds in almost any light that's reasonable. The little bit of noise produced is easily eliminated and sharp images are great.
It depends on what resuts you want. High shutter speeds may reduce camera movement, but also freeze motion. If you want a blurred effect obtainable with a slow shutterspeed, such as when shooting moving water or some sports (e.g. a blurred tennis racket) you would want image stabilization or a tripod.
Also, if you want great depth of field (f/11, f/16) in anything but bright light you'll probably need slower shutter speeds even at higher ISO's, and image stabilization becomes desirable.
I also question the term "any light that's reasonable." I find all light reasonable depending on the effect I want. After using image stabilization for the last 10 years, I would not leave home without it.