I can certainly empathise with the whole re-writes of passages. Back when I was invovled in PBEM's. I would often go back and tweek parts or re-write what I had previously written.
Perhaps that was in part because I tended to write in a flow and then go back and change were I felt I needed to. It was quite good fun and at times I still wasn't fully happy with the way it turned out. But with the nature of PBEM perhaps much like writing is that you had a deadline of sorts in the case of the PBEM it was one post a week that was expected. Some of my best experiances where writing with other parties.
It wasn't for a ST novel but for an SG-1 novel, I collaberated with someone from the PBEM to sumbit an example of work and an outline for a novel. Suffice to say it was challanging to both her and I. It was still fun however.