Indeed, I have noticed weak video on the ipad when flying the Spark, not too bad so far, but so far I've only flown it close, and only twice vs Mavic Pro a couple of hundred times.OTG only eliminates Wifi between the RC and Smartphone. The drone is using Wifi for flight control and video downlink.
I think it can have a place in my life, it's so small and quick to get in the air . . . but surprisingly noisy compared to the MP with 8331 props.