My ex and I sat together in a room with the mediator. We each met privately with our own outside lawyers in between the meetings we had with the mediator. (We COULD have had our outside lawyers in the room with the mediator but that would likely have been expensive and unnecessary in our case).
I do think mediation is the way to go ASSUMING that both parties can be civil and that one party is not so weak that they would always give in.
Having our own outside attorneys gave both myself and my ex a sounding board and the assurance that we weren't getting totally taken advantage of (let's face it - both parties will feel like they got shortchanged if it's a fair divorce lol). I'm sure my ex would have been more unreasonable if he hadn't had an attorney outside to tell him that the deal was fair.