I think KDE 4 may disappoint some long date KDE users for some features that were lost, transformed, replaced or still don't work.
In my case, since I am so lazy to read a help reference, it took me some time to discover that the columns feature in Dolphin. It does similar task that the tree feature in Konqueror but in a more visual-friendly way.
The tree feature allowed to be show more information about a file and more directories to be opened but you have to do much scroll work in order to see all that.
The columns allow you to open directories in more levels without clearness loss. I think it is a sample that summarize the differences between KDE 4 and 3.3.x right now: more easiness for sight but less functionality.
And after all I've said, complying with a five century's tradition in my country, I will suggest that KDE help would came with a kind of migration guide for KDE 3.5.x users, with a list of "the way you used to do that formerly" and "the way you do that now".