I have just published an updated version of my Dropbox client on CodePlex. You can download it here. I have rewritten the library from scratch (took out all dependencies - Json.Net and Hammock, added the download progress event and a lot of other things that I cannot even remember). It's faster, better and it's the exact same library I am using in my Dropbox application . I really hope that it will be useful for your projects and hope your projects will not be something similar to Boxfiles.
That's all folks!
P.S. It doesn't have a test project, but you can use the one in the first release. It should be easy to use and pretty intuitive. If you find bugs or want to improve the library please let me know