Part of the problem is that there is no polished solo test feature like in skype. So unless people get on earlier and do a 'test test test' type call and get someone's feedback, they might run into issues when they decide to speak. Bytemaster was fine the first time, but on the third try it took him several minutes to get something corrected. You'd need to work with speakers ahead of time I think.
The other thing is that you might wish to tell people to mute themselves/push to talk. Make it VERY clear when you announce so you don't get people joining with instant feedback.
Also, if the person is speaking much, they should turn off that typed chat -> voice synth. It might be ok in some situations, but it should not be on as a default. It throws off the person talking when they start hearing Robby the Robot talking over them. The typed chat should not be intrusive to the main speakers.