Although I can certainly get great action photos by planning my shots and pre-focusing, having usable continuous autofocus makes a camera much, much more versatile to me. But so far, I've been disappointed with the continuous autofocus performance of almost every mirrorless camera I've used.* Even with these new hybrid AF systems, I still get better continuous autofocus results from most entry-level DSLRs. I was hoping the NX30 would be an exception to that rule.
Unfortunately, the NX30 falls into the disappointing category when it comes to continuous autofocus performance. I have about twenty years of experience shooting high-speed action with autofocus SLRs, including motorsports, cycling, snow sports, etc. With the DSLRs I usually use, I get consistent in-focus high-speed bursts of subjects accelerating towards me. That was not the case with the NX30, though.
I tried all kinds of variations in focus area, point position and focal length, but no matter what I did, the camera's AF system wasn't able to keep up with even relatively slow-moving mountain bikers -- at least not with the 18-55mm and 55-250mm zoom lenses I had for testing. As a control, I also tried shooting bursts as I walked towards a brick wall in bright sunlight. That's a focusing task I think the camera should handle easily. At walking speeds, I did get better results, especially with the 18-55mm kit lens, but they still weren't good enough for me to risk with serious, irreplaceable photo opportunities.
The bottom line is that I need consistent, predictable and accurate performance, and the NX30's continuous autofocus did not provide that -- at least not for the mountain biking that I shoot most of the time. I can't afford to gamble with iffy autofocus. To be fair, the NX30's continuous AF was on-par with most mirrorless cameras I've used, and I was still able to get plenty of great action photos using single AF, planning my shots and pre-focusing. For any kind of racing or paid commercial work, though, I'd leave the NX30 at home and bring one of my trustworthy DSLRs.