I'll have to go with "completely dependent on all the people involved".
My first time just hurt. So did the second time. Third time was fine. I think if you can let go of any expectations, if you trust your partners, and are able to laugh at the moments of awkwardness (because they will happen), then go for it.
If you're very nervous, there are any unresolved issues or undercurrents in the relationship, etc., then sex should wait, regardless of how many people are involved. The first time brings a boatload of emotions.