I have found a used one in fact, planning on getting it tomorrow. I am going to bring my own K10D to see if the AF works properly, etc. etc. on my own camera.
Sorry my original post (which I reread) has some typos.
Originally posted by Pentakun The Pentax new is about $200 more than either a new Tamron or Sigma; or $200 more than either of the two.
It should have read "The Pentax new is about $200 more than either a new Tamron or Sigma; or $300 more than either of the two when buying used."
As was mentioned, I wonder if Pentax would outshine the Sigma, and justify the $300 - $200 price difference? I guess we all wondering and it's too soon to tell since it hasn't even come out yet.
I'm planning on getting the Sigma now, since the price is right and I want to take it on vacation from Aug 1. After that, I can study the Pentax version.