I just received my new Sigma 24-60 f/2.8 EX and it has a couple of focus problems. First, it back-focuses pretty bad at 60mm. Second it has problems focusing accurately at all FL when I use my 430EX flash emitting focus assist.Now I called the vendor and they will gladly exchange for a new lens. I also called Sigma Service and they said send it in no problem.My question is, is it worth it to do the exchange and maybe get another lens with the same or different problems? Or should I just send this one in to Sigma and get it repaired.I do have to pay to have it shipped for the exchange. I don't want to pay to get another bad copy and then have to pay another shipping charge to send it to Sigma. Not to mention the added lead-time to fix the problem. Any advice??

See responses in this thread: http://forums.dpreview.com/forums/readflat.asp?forum=1019&thread=24817395 Looks like you Sigma needs to be rechipped. I going to send mine in.Edit: I just noticed that you already saw this post. In my opinion, from the retailer you will get another copy that would need to be rechipped since it is not a copy variation but a design flaw.