I have used Jitsi. Last week I did a few pairing sessions where the both of us were sharing our screens and still had our webcams on in the corner and it was awesome.

We tried to do a standup with (I think) 8 people and it was terrible - people would randomly not get any audio for stretches of time, video would get choppy or lost completely, it was not pleasant.

I will keep using it for pairing since I haven't found another tool that gives me that kind of flexibility and it was in fact very good. I believe the whole experience is limited by the connection quality of the worst participant.