[wanderr]

It keeps the upstream history cleaner at the expense of being locally historically correct. In my opinion the nice thing about having everyone rebase onto upstream is that when their changes get merged into upstream, upstream's history shows an accurate linear representation of when a piece of code was accepted into upstream, which to me is far more important than having an accurate local history.

[Davertron]

Great point. One of the more confusing things about looking at the upstream logs when not using rebase is that they are (by default) in chronological order. It does seem like it would be more useful to have commits upstream show in the order they were merged in.