Are you kidding? It's one of Canon's sharpest, if not the sharpest, lens at f/2. I use it for indoor sports or even for outdoor if I know I don't want to shoot shorter than 200. My copy is sharper (and I can tell when I print 8x10) than the 70-200L II IS at 200. When I do golf I take my 400 f/2.8, 200 f/2, and 70-200.
Completely agree, nothing sharper in the range (200mm), murders the 70-200f/2.8 II and this is no slouch of a Lens either, but the 200f/2 is again a bit of a specialist Lens, like the 85f/1.2 or the 135f/2, having said that I use the 200f/2 a lot more than either the 85 or the 135, the 200f/2 @ f/2 is just Sharp, Crisp, Clear and a complete pleasure to use.
The 300f/2.8 II is also a wonderfully sharp Lens, I wouldn't like to pick between these two lenses re sharpness, they are both just about perfect, but the 200 is f/2, you want to clear a background, this is your Lens.
And I've shot the Nikon 200f/2 on the D800 just for comparison, and there's not a hope in hell the Nikon 200 is sharper, but that's an opinion and subjective, 1Dx + Canon 200f/2, Sharpness & Bokeh heaven.
Use ?? anything that requires 200mm and a perfectly blurred background, portraits of course, but I've used this Lens on Safari, just a great Lens