The UI and features allowed for all of these things, but guided you on none of them. There were no first-class workflows for any of the possible use cases.
No, I don't want a conversation to spring up anywhere in the middle of a document. I want the workflows and UI for edits, suggestions, and comments to be distinct and guide me and all of my collaborators towards clear and efficient ways of accomplishing my goals. With Wave we had to invent our own conventions for each task. That's why everyone shrugged and left.
Wave as an enabling technology and platform for apps would have been great though. Make it easy to repackage the basic features in a tailored UI for chat, email, docs, etc... Maybe even leave in the general interface to allow for hybrid apps, universal inbox, etc. At least the specific apps would have avoided confusion on what Wave is actually for.