Hehe, ok, a mod discussion.
To give you some insights on how i did it. I simply copied over all of my configuration data. Most of the Apps did recognize it and it worked well. Some though had some rough edges, and some don't even exist on KDE4, but that's okay, i can use the KDE3-version of them inside KDE4.
But the greatest problem is the well known problem: not enough manpower. Not planning, but manpower. There will always be little parts that are overlooked but nevertheless important. So it's up to the user to tell us what needs to be done to make KDE rock It's not a big deal. Go to bugs.kde.org, search for an entry, that already fits your needs. If it doesn't exist, feel free to open a new Wishlist-item. YOU as a user can help to make KDE become a great DE.
Nevertheless, to give all the visitors an idea, at this point, OhReally is the Guy for KDE3.x and i am the Guy for 4.x. We both love KDE, for sure. We don't agree in all points, but we try our best to solve all problems coming up.