Just the sleeve? Or the K2 kinetic arm? I love that recent topics have come up where I have some experience. So my kid decided to buy the K2 kinetic arm after his injury. He got it on sale for less than $200. He finds it very comfortable and not intrusive at all to wear. I suspect it might be a little uncomfortable if it's really warm outside.
What do I think in terms of injury protection? Probably doesn't work. Even though the fit is as good as it gets, there are some subtle areas of slackness. I think a good K tape job over the areas of concern is probably more effective. And that might still be voo doo. But if you want to do something, I would meet with a trainer and ask what type of k tape pattern would support your area of concern and then do that before games. Remember to apply to clean dry skin. Maybe use rubbing alcohol to clean beforehand.