I bought the GX10 and loved it. I liked Samsung's controls design a little better than the Pentax version of this camera. Plus I never saw the point of yet another proprietary RAW format. Samsung's use of the Adobe RAW format just meant one less step. When the GX20 came out, I responded to the lure of the new CMOS sensor and half again more image size with the GX20, The potential flexibility of having an Xsync connection that might allow me to experiment with and maybe give a new lease on life to a bunch of older lighting equipment also had appeal.
I was not disappointed. Same great camera just better.
The Kit lens however is much better. I tried it and left it in the box when I bought the GX10, but the lens that came with the GX10 is improved, I'm using it this time. It has saved me from always using the much heavier 18-250 zoom, and maybe even from buying two very expensive 21mm and 31mm primes. The Kit lens is not their peer in image quality, but it is smaller lighter and enough better to make me think twice before parting with all that money for the now smaller increment in image quality.