It’s my understanding that you can install KDE 3.5, if you like. I couldn’t get my @#$#! NVidia drivers to work with 11.1, so I haven’t actually done that myself. YMMV. I’m still on 10.3.
As for KDE 4 vs. 3, there are flame wars all over the Web about that. The “4” adherents are insisting that it’s the future, the “3” diehards holler that “4” has been so dumbed-down as to be unusable. 
Just for the record, I’m in the “3” camp. I despise Dolphin, for starters, and I can’t get Konqueror to work properly as a file browser under “4.” I get faults and crashes. I miss my mouse-over previews, one of the coolest things ever put into a desktop. I also want some configuration options that have been left out of KDE 4.
(One example, admittedly personal taste: I like my 4 desktops to be totally separate, complete with different wallpapers, and I do NOT display the icons from other desktops. I can get the icons to do what I want in “4,” but not the wallpapers.)
(Call me anal, but this has kept me from Gnome all these years – that, and the fact that they still use the 1990’s style “.” and “…” in the file listing dialogs instead of the far more intuitive “up,” “back” and etc. buttons.)
I don’t know when GUI designers are going to figure out that LAYERED config options are the way to go. When a new user first brings up the config dialogs, sure, keep it simple. But don’t just REMOVE the more advanced options! Put a button on there (make it small, if you insist) that says, “Advanced Geek Stuff” or something.
Bottom line: those of us who liked KDE 3 should be able to make KDE 4 look and behave the same way. If they’d do that, I’d have no complaints.
Again: my opinion and YMMV.