I mortgaged my future with KDE several years ago, and the KDE project "went off the rails" with v4. My usual ways of working weren't improved with new benefits - the entire rug was pulled out from under me. All my effort in learning KDE stuff, and putting my data in KDE apps was wasted, as I had to spend time to migrate all that data to other apps. I'm being somewhat sarcastic, but also honest - I used KDE as a prima…
You don't need to see KDE SC 4 as the successor of KDE 3 even if they have the same name. Just use http://www.trinitydesktop.org/
KDE people just reused the name because of marketing.