Cracks me up when I see people complaining about slow AF and weather sealing on a portrait lens. It was never meant to be a fast, do it all warrior. If you want to shoot sports, don't buy a studio portrait lens. If you buy this lens for the wrong reasons, you can't complain about it. For what it was meant to do, there's just nothing better and that's that.
Well, it's a lot of money to be stuffing into an environmental portrait lens (it's definitely not a good choice for a studio portrait lens -- that award goes to the 28-135) that isn't weather sealed and is tough to use for candids. I personally think I could myself picking it up if it had better AF/IS/sealing.