CRDTs have sounded pretty interesting, but I haven't actually learned anything about them yet, so this is my first time reading any details about one. I have to say, I'm very underwhelmed. What is the difference between a lww-element-set and just a set? The only thing I can think of is that the timestamp is delivered as part of the payload of the add/remove operations, rather than it being tied to the time wherever the set lives. Because the systems submitting the operations all have their own idea of the current time, you still get the same effect as in a generally lww system unless you have somewhere a single system handing out unique timestamps.
If I understand this correctly, CRDTs allow you to cope with multiple add/remove operations for the same element on different nodes by assembling them into a meaningful order without relying on timestamp ordering.