Wow, quite a bit of feedback for versions of KDE and Kubuntu that are nearly 10 years old.
As such I think most of the feedback is rather out-of date (though we sure appreciate seeing the positive feedback). As impressive as KDE 4.1 was (at least as compared to 4.0, and possible to 3.5, though that comparison was a mixed bag as it wasn't until around 4.4 or so that the 4.x series was really able to fully replace the 3.x series), there have been great strides made through the years with the 4.x series finally ending with 4.14 which has been really rock-solid before starting down the 5.x series which has also seen similarly great strides (and setbacks, though not nearly as bad as 3.5 to 4.x was).

So the question is that as I assume you've updated your system a few times between when you wrote this and now, what still remains unanswered in your mind here?

As to your questions about Kubuntu's ideals, we've seen through the years a number of desktop-specific Ubuntu derivatives. The goals for each one are generally to provide the best experience for people who want to use that desktop. Having separate distros allows Canonical to focus primarily on their core offering and then having enthusiasts who know the other desktops customize their derivatives to the best of their ability. Over the years Kubuntu (after getting past some of the early versions of KDE 4) has provided one of the best KDE experiences on the desktop (second possibly only to OpenSuse, and a few other KDE focused distros which have changed over time).