I bought this lens as I wanted a 'long' lens for occasional use, and couldn't afford the price of an EF Prime lens, (over ten times more expensive). And this is only a my views on using it half a dozen times so far.
I was hoping this lens would be good, but not exceptional given it's price point. Having read several good reviews online it sounded worth the investment, and I'm not disappointed.
I use it on a EOS R5, (which I've not had that long), and am v impressed. I went to a local country park last week to try it out on some wildlife, which I've never shot before, and am delighted with it's performance, as hopefully the accompanying images show.
Just bear in mind a 600mm lens is not your average 'every day' lens, and like all long lenses will be susceptible to heat haze and general crap in the atmosphere.
What more can I say, if I remember I'll add some more comments in a month or two. 9.5 out of 10 from me.