Originally posted by adwb "No pro with any manners would use a 50mm to do portraits" - uh, the DA* 55 is based on the FA* 85. It was created at 55mm because with an APS-C sensor that length comes out to around 85mm (aperture has it at 82mm). I know what you are getting at, but the 80-85mm range is notorious for the preferred full frame look for portraits. Sure my 3rd picture has a hint of distortion, but that is because it was intentional. Sure your website you listed doesn't have 50mm "in sight", but explain to me why the 85mm was the go to lens on film? Why is that Pentax's storied portrait lenses are 85 and 77? You can't tell me Canon or Nikon made anything better for portraits than those two lenses. The 55 is from that heritage and splitting those two right in the middle at 82mm on APS-C. You could make the argument that "pros" don't use APS-C, but then I would ask you why you even commented on someone's thread entitled "K30 with 18-135WR".
Sure the 135MM does a great job of subject isolation, but I have never had a subject say "Wow, you are too close". Someone with a K30 and a 18-135WR asking about portraits is not looking to get published professionally next week. They are trying to learn the trade - and traditionally that 80-85 range is pretty darn popular still to this day.
Back to the OP's comments and Adam's - the DA 50 1.8 is a great lens for an extremely excellent price for portraits. The DA 55* is, in my opinion, the best lens you can get for portraits on a Pentax system. The 50 1.8 is the best you can get for the price point, by far.