My point of view is probably slightly different since my background is motion and not stills. Everything being equal, my philosophy is always get the fastest glass you can afford. I don't get or agree with the new viewpoint everyone is taking with slower lenses (and slower lenses with IS) just because cameras can now shoot at crazy-high ISO's and still produce clean results. An f/4 lens shot with a camera than can jack the ISO and still be clean and achieve the proper exposure is not the same as an f/2.8 or f/1.4 or f/1.2 lens. Aperture is for more than just exposure.