I have been using nothing but manual primes on the NX1 since 2014. When I had to shoot a wedding in 2015, I decided to rent the 50-150 and take a chance. Overall, the 50-150 performed well enough in a dimly lit church and reception hall. My settings were around f/2.8-f/5.6, ISO 400-2000, and shutter 1/50-1/100 using burst rarely. The photo AF is not up to par with your classic 70-200 f/2.8 Canikon lenses but it did deliver when I needed it to.
The 50-150 photo AF definitely struggles with faster movement in low light/high iso and is literally hit or miss. With slight movement it was pretty accurate most of the time. The pastor did not allow any flash during the ceremony which would have helped my shots big time (grain/noise and photo AF). Using the 50-150 outside was a dream (nice and sunny) and it didn't miss anything.
On a different note, the one thing I really enjoy about the 50-150 and NX1 combo is the video capability. During the wedding, I also shot about 30 minutes of 4k footage using the video AF and OIS. The 50-150 video AF and OIS is the best I have used to date. The video AF actually out performed the photo AF by a large margin (shooting the same scene) and this is while handheld at high focal lengths with high iso.
In conclusion from my experience on a paid gig, did the 50-150 perform well enough for photo AF in dark and fast situations? Yes. Did it perform as well as other popular lens/body combos? No. Would I use it again for a wedding? If I can use my flash or it is a sunny event, Yes.
Funny side note, as much as they liked the photos I think they liked the Bluray more.
A few shots from the wedding I spoke of.