I prefer the free for all type sessions to any other format.

One problem I have noticed in formats that use rotation based on where people sit (and I've seen this happen on singers nights at folk clubs where the situation can be worse if each singer does 3) is that people who like the same type of songs or tunes are often friends who sit together. End result could be 4 dirges followed by 4 instrumentals where alternating dirges and tunes would be preferable.

Jon