I have the original 16-35 f/2.8L and it is one of my favourite lenses. I am currently using it to shoot motorcycle trials, where I can get in real close to the action and use the wide angle to impart a really dramatic look, albeit at the risk of being flattened ...
It's hard for me to believe that the later versions produce better pictures unless you're printing large format, which I don't. The colour rendition, sharpness and reliability are bloody fantastic, to be honest.
I shoot each event with the 16-35, a 24-105 and a 70-200, all f/2.8 versions. I occasionally use a 1.4x TC with the long zoom. I generally start off with the 24-105 until I know my way around the sections, which are varied and usually dispersed within a forest. I then switch between the 16-35 and 70-200 and, when I'm processing the results, I really look forward to seeing the shots taken with the latter two lenses.
