We've used it intensively here at OpenForce. It doesn't scale well at all. This is partly due to BLOB storage (which is a hack, we all admit it), but mostly to some heinous complex queries in there that were never meant to be so complex.
Plus, there's my philosophy that storing these files in the database is a mediocre idea at best. There is no need for transactional control over the file content. Thus, we have built new-file-storage, which stores all files in the filesystem, has a more logical permission scheme (permissions linked to files instead of versions of files), and is generally much faster. I'm happy to distribute this code, I just didn't want to add yet another new module to the distribution.
