A friend of mine says Xanadu got quite a bit further, but failed hard at the end because they'd not bothered to do and keep viable the total end to end use case. Specially, to actually interact with the system and display a document was so hard and cumbersome it never had a chance of being adopted (by pretty much anyone, let alone widely), whatever other problems there might have been with the project.
Yeah, quasi-stealth mode vs. bazaar was a killer.