@auspex Yes, I've tried it but it has been a while back, and if I recall correctly, if the books are already present the goodreads site, it tries to help you match them up and, with only a few exceptions, it can usually do it.
I still found it to cumbersome and time consuming to do regularly. To me, shelves are analogous to tags in Calibre, others may disagree but that is how I see it and how I use it. Two-way sync would be the best for me because I could then manage all of my books in Calibre and just sync those changes to goodreads all at once. However, I may occasionally be on the site and change the rating on a book or the shelving. It would really nice if the goodreads sync plugin in calibre could notice this and update Calibre accordingly. This is just pie-in-the-sky though, I'd be thrilled if I could only create shelves from my tags.