Does it help other multicast services like OSPF and NTP, or just to PIM and IGMP?
Can we forget about NBMA then?
Yes, on point-to-point links.
what about P2MP??
I think it is the same as before. I get a more stable result with OSPF if I set DR on AP and disable BDR at all. NBMA is even more stable, but does not work correctly on versions before 5.x