I have a GX-10 and am really pleased with it. For me, I bought it instead of the Pentax because: it was cheaper, it came with a two year guarantee and, according to the reviews, the only physical difference is that the Samsung menus are easier to understand. And, having read side-by-side reviews of the Samsung and Pentax lenses, it's clear that they are identical in construction and performance. And the Samsung lens mount is the same as the Pentax, so any lens that can be used on a K10D can be used on a GX-10.

Unless I could easily stretch to a K20D, I'd still go for the GX-10. I bought the twin lens kit at a very good price and am pleased that, in addition to the standard lens, I also have the 50-200mm telephoto. This might be worth you looking into.