Wed 02-Jan-13 08:19 AM | edited Wed 02-Jan-13 08:21 AM by briantilley
As Jon says, there are situations when you need the f/2.8 aperture - and sometimes even that isn't really fast enough!
For my work with amateur stage productions, I'm always at maximum aperture, my shutter speed is a slow as I can get away without risking motion blur in the performers, and my ISO (on Auto) is often too high for comfort. Typical values when the lights are low are f/2.8, 1/160th and ISO 51,200. Swap out f/2.8 for f/4 and something else has to give.
I'm sure the new f/4 lens has great image quality and handling, but for me it couldn't completely replace the f/2.8 lens.
Having said all that, I AM looking to acquire a 70-200mm f/4G VR - but (with a TC-14 when required) as a replacement for my 70-300mm f/4.5-5.6G VR