About Debian I disagree on one point : it's less complicated than what peoples often think, and there are lots of resources for Debian on Internet…but for Ubuntu too. And Ubuntu docs can be applied to Debian most of the time.
Yes, there are a lot of resources for Debian, and community in general is helpful. But even though I'm using it for quite a while already, small issues here and there in testing make me wonder how good can a non technical person handle them. Even for me this can take time (going to the wiki, searching for answers and tricks and so on).
Since Debian testing is a rolling distro, there are issues which come along with that. A simple example: when you do system upgrade, what is the preferred way? There is no one prescribed method. In KDE there is apper for GUI, but I use apt-get update && apt-get dist-upgrade. And someone (not the system) has to remind you to install apt-listbugs and apt-listchanges which will warn you if any particular update contains a serious reported bug or regression. One has to then figure out how to prevent that package from upgrading if necessary. How would a non technical person know anything about this by default? However Debain testing is still positioned as to be suitable for everyone, and to some degree it is.
Another thing, upgrades often leave behind automated packages which aren't needed, and it proposes to call apt-get autoremove on them. That's fine, but doing that leaves behind configuration files. Who could have known that one has to run it as apt-get autoremove --purge... I just found out about it very recently. I still consider Debian to be a very worthy choice though, if one is willing to invest time in learning it, as various things come along.
About KDE…for my part, I just dislike it and find it unintuitive. Gnome 2 was very fine before. Gnome 3 was not very mature at start but become pretty good now. Or there is Enlightenment (E17), very light, beautiful and so on.
Or for peoples which like to configure things on a very precise way : Openbox, Fluxbox, ion3 and so on.
For myself, I just now use Gnome 3 most of the time. It works great out-of-the-box, you can add couple of extensions if needed and it's very ergonomic at my point of view :)
It's the flexibility of KDE that I like, and their proper approach to design. They don't pile all this mobile nonsense in the desktop interfaces, they have Plasma Active as a separate design approach for tablets. Gnome 3 unfortunately suffered from introducing excessive minimalism driven by the retrofitting mobile ideas into the desktop interface.