Hello,
I'm using the nx1 for stills for my job and I find the AF extremely bad, not in line to what reviews said. My old Canon 550D is much faster and better in low light.
I'm using it on the ski slopes with the 18-200mm with very good light and sometimes it misses the focus or is not that fast. Tonight i tried to use it indoors in a very good lit restaurant. At 18 till 70mm it would focus eventually, beyond it just hunts for focus and then give up, while any DSLR would focus instantly. I thought that with phase detection mirrorless cameras would behave the same as DSLR but I guess I was wrong.
I tried to use every single focus option but for certain situations it just won't focus at all like if you're focussing on a white wall.