I've had several 70-200s before, one being the f4L. it was nice to have and satisfied my L desires, but it on crop the length and speed were so restricting that I had to find excuses to use it to justify keeping it (which I eventually couldn't). As nyy says, strictly outdoor on a sunny day lens.
I have recently fallen love with the length again on full frame though, and gave in on a 2.8 model from sigma. Totally different lens on FF.