I've just upgraded openSUSE 11.2 to KDE 4.4. after adding http://download.opensuse.org/repositories/KDE:/KDE4:/Factory:/Desktop/openSUSE_11.2/ to my repositories. The upgrade itself caused no problems. Everything seems to work as it should - with one exception: I got a message that Nepomuk is disabled. I have to investigate that.
The Nepomuk problem seems to be solved. I found the decisive hint on http://forum.kde.org/viewtopic.php?f=20&t=84500&start=20#p143959 : Under ~/.kde4/share/apps/nepomuk/repository/main/data/ I had to manually create the subfolder redland. After restarting Nepomuk and Strigi everything works flawlessly.
The classical KMenu. Hm - quite frankly, I've never thought about using anything else What about you?
Just in case that you got error messages from Akonadi like this one: http://img80.imageshack.us/i/bildschirmfoto1t.png/ I found a solution here. Regarding Akonadi, this and this sites also stress its importance and present some troubleshooting tips.
I'm just kidding of course. But you should give it a go someday (Lancelot), it's very configurable, including its size.
I've actually gone back to 3.5 for the time being. It feels quite retro-cool to be running it. So light and fast I just can't give it up fall time just yet. Although it's fast kde4 still feels somewhat bloated, i'm struggling to warm to it. It's still lacking some of the simple functionality that 3 provides. I'll probably wait until 4 is in stable before switching full time now, if at all. LXDE seems to be closer to what I want DE wise than kde4. So perhaps when Debian drops 3 I will drop kde all together.