I haven't found one and I really wonder if everybody rolls their own sync solution.
> The one thing I dislike about couchdb is the default "user-per-db" model.
Why exactly? I think the overhead of the DBs is rather small. It's not like having a MySQL DB for every user ;)
Also, you can achieve something like "global data" as well: Either replicate from users' DBs to a shared DB or maybe make some kind of "system" user that has access to the users' DBs. I'm not an expert, but that's what I figured out so far with my limited experience.