I've used Zoom for the past year and a half on a course which has students from South Africa, Australia, New Zealand, Hong Kong and the UK. It's not complicated and quite high quality.
The usage of Zoom worldwide has gone up by something like 533% because of the Coronavirus pandemic.
Trolls are zoombombing and inserting things like porn films into meetings. I haven't seen anything like that yet, but Zoom allows you to set up a password,
It is also being used by organizations like NA and AA. There has been the occasional idiot in a 12-Step meeting who wants to take charge and won't shut up. They can, however, be muted and then shown out of the virtual door.
Jack