This whole debate is sad really. From my point of view as a KDE user by choice (as opposed to having to use MS for work) I read about the release of KDE 4.0 and CLEARLY got the message that it was primarily a developer release and wouldn't suit my needs. I wouldn't have said that the KDE 4.0 release was half-baked. There appears to be such a fine line between release early and get flamed!!! Personally, I think the KDE devs and others did a good job of communicating to ME what to expect of 4.0.
Furthermore, Ubuntu got heavily criticised (I seem to recall) for not doing a Kubuntu 8.04 LTS release based on 4.0 - feeling that 3.5 would be too old to be maintained for three years yet 4.0 was too raw to support.
They clearly got the message about 4.0. I don't know why Fedora chose to switch to 4.0 without easy recourse to 3.5, but I know they have pushed other technologies and got angry responses from their users in the past.
However, I think there is a place for distros to push the envelope and make bleeding edge software default to give users the ability to test and develop. Perhaps Fedora didn't/haven't communicated to their users the implications of switching to their bleeding edge release well enough. It seems to me that Kubuntu/Mandriva and others knew enough to make KDE 4.0 optional.