I really did like Google Wave and I'd love to see someone try the concept again, but it did have problems. Among other things, it really was quite buggy. Early on, this was understandable: they launched the product at a very early stage, which IMO is fine as long as you warn users what they're getting into. But as I recall, it never really stopped being buggy.
They gave up on the prototype and added the live collaboration features to Google Docs instead. They left the mixed chat component behind pretty badly but they did build a good concurrently edited word processor. Does anyone else remember sending docx files around by email for revisions in Track Changes mode?
Notion has some good ideas but to me it's no Wave! Wave, to me, just felt very seamless and free-form/flexible, in terms of how you could go from chatting to planning to collaborative writing and editing.
