I think what I'm eventually going to have to do is roll my own. I don't need crazy complexity, but I do want some features nothing seems to have. I want the bulk editing that's only on goodreads, and I really want series to be first class citizens. That means series nesting in other series and being able to have a blurb/rating for a series instead of each individual entry, mostly. I just haven't got to it yet.
I don't necessarily have to have the metadata all the public social network style tools use to combine everyone's input to one book object, though I definitely understand how it's frustrating for services to lose information when you import your lists. But organization tools are critical to me.