This past week I had the wonderful experience of having a cowriter come visit for a writing retreat. While we had lots of fun, we also got an impressive amount of writing done.
I'm not sure if this is the case for everyone, but I find that there's a magic when two writers share a story. What emerges is a tale that neither would have told alone, in a voice that doesn't belong to one or the other.
It's a revelation to be able to sit around and brainstorm plot points over lunch, then dive into the edits after dessert is over. Or to run into a problem, argue it out, and have the solution in minutes.
Sometimes, 1+1>2.