Excuse me but the IS isn't almost
useless for sports it IS useless. If you have IS, turn it off
. The IS takes longer to react and focus. It jumps and shifts. Not opinion, just fact.IS Shift Example
This is what happens as you focus with the IS. Extreme example of the IS jumping at the exact instant that the shutter released. And it does slow down auto-focus.
Opinion: I had the f/2.8 IS USM version and sold it, now carry the f/4 non-IS version (bought used, for sports) Just as clear and sharp. Used the spare money for a 100-400 and a 400mm f/5.6
Cute little lens, just as good image quality. Consider all of the rest about f-stop and features.
Here's a breakdown that I didn't understand at first. f/2.8 comes with a tripod ring, included and a nice white Canon case. F/4 comes with the grey felt pull string bag and no tripod ring. Cost savings are noticeable.
IS models are weather protected, Non-IS aren't. You pay about $1000 more for the IS.
You don't need a tripod ring and can easily hand hold the f/4, but the f/2.8 you may want some support or what I like is a monopod.