I used it and wasn't really impressed. I felt it was a RF Poser's fashion camera. it does take pretty nice pics tho.
Also from further up I don't think I could ever call the build quality of Sigma lenses "good". Unless maybe I was comparing it to a Holga or something.
Some of them have pretty good optical properties in spite of their build quality. In almost all cases Tamron and Tokina are better tho - still talking about IQ. I think Cosina is probably the best company around these days who are dealing with µ4/3. They made many of the Zeiss, Voigtlander and other famous lenses we all love so much and which actually do have a decent build quality. If I wanted to pay out for a 200mm or 300mm prime (or even a zoom) I would hope it would be one from them. Hopefully something in Superachromat or Apochromatic of speeds 2.5 or more. I recently tried the Cosina/Voigtlander APO Lanthar 125/2.5 Macro (1:1) and it was like using an entirely different camera. It was as if my GH1 had suddenly become a $3k pro body. I was amazed! It beat out every other Zeiss, all other Nikkors, Rokkors, Minoltas, Lumixes, Canons, Zuikos, Tamrons, Tokinas, and Sigmas I've ever tried. And I've tried most or the more famous ones. It was a clear smack-down, no questions! That's what we need. Another 200 or 300 from Sigma would likely only be a duplication of the extremely poor Lumix we already have. I want something nice!
With Cosina already making a few µ4/3 lenses in the Voigtlander family I would hope for a long lens from them - not Sigma.