I'm a big user and advocate of Zotero, but "it just works" is not a description that I'd say applies to it. It works kind of reasonably okay most of the time, and you get a feel for where and how you have to give a thump the times when it's not working the way it's supposed to, but it has its flaws. Unfortunately, it's also gotten harder to build, which means more difficult for people to get involved to contribute changes.