I used KDE 4 from beta up to 4.6. I can't say anything about 4.7 or 4.8, but from what I've seen, KDE 4 was very unstable, and it was such a sudden and huge change that even now, when people tell me, "Oh, it's improving now," I can't get myself to go back. It would be one thing if all the changes were more gradual, but such a sudden change is a good way to drive away existing users and will give way to projects like TDE. If KDE 4's stability is actually improving, you might attract new users, or existing users who liked the changes (from what I personally have seen, not many existing users do like the changes, regardless of stability).
From our perspective (or at least from my own), the sudden changes and instability make it seem as though the KDE 4 devs don't care about the users anymore. However, since I'm not a KDE 4 dev, I can't say whether or not my "KDE devs don't care" view is true. It could very well be that they do care. But it certainly would have made sense to delay the 4.0 release, regardless of what changes took place. In fact, when making such immense changes, a release date isn't a good idea until the devs know for sure that they can make a stable release.
I personally have not been as satisfied with TDE as I was with KDE 3.5.10, new glitches have popped up that I don't remember being there. I haven't noticed any issues with Kicker, though. The issues I have noticed are already in the bug tracker, and there seems to be a concensus that a more stringent QA cycle is needed, hence why I am still with TDE: I am willing to sit it out, and see if things improve, and I am certainly not the impatient type when it comes to projects run by a small dev team.
So now that you know the perspective of one lone user, perhaps you can try to understand that perspective and the perspectives of the others posting to this thread?
Ark Linux webmaster