Let me be the first to say – IT DEPENDS.
Money is an issue for me. I am a college student. I got a used f/4 non-IS for under $500. If money is not an issue for you, go for it – get the extra stop in the 2.8.
You may want the 2.8 for the lower depth of field, but you can get fantastic depth of field with a 70-200 without paying a thousand more dollars by using a cropped sensor camera, shooting towards the 200mm end, and positioning you and your subject correctly.
Image stabilization, in most cases, would be useless for me since I’m often shooting outdoors with a shutter speed of 1/80 or higher.
Case in point: Brad Wing, Steelers punter, signing autographs