I use a mobile BP every time, and never have checked bags. On many trips with CX/KA, long and short haul, I've only had a mobile BP rejected once, and that was in Singapore - the dragon guarding the security area made me go and print it before she would let me through. Not sure if that was an official policy or just her, but on previous and subsequent trips through Singapore they had no problem with my mobile BP.

Never had a problem with mobile BP at the gate anywhere, apart from the aforementioned re-entering of passport details every time, which I've now solved thanks to this thread - I just do it when I arrive at the lounge instead and boarding is much smoother now!