Debian has KDE 4.3 packages in Sid. If you are running Debian’s testing then, it’s not too hard to get it installed. FYI: Debian’s Testing version is equivalent to running a Ubuntu distro only the bugs are (on average) fixed faster.

1. Add Sid repo’s to your sources.list
2 create a /etc/apt/preferences file and pin testing at a higher priority than Sid.
3. Apt-get -t sid install kde-minimal
4. logout of your display manager. You should have the option to restart the display system (X).

After restarting X, you should be good to go.

To enable all of the desktop effects and eye candy:
You need to modify your xorg.conf to enable compositing. This is not rocket science, but depends entirely on your hardware, reading the man page (ex. man nv) and finding some examples on the Internet. All of which are readily available.

First, enable compositing by opening System Settings->Desktop.
You should see the enable/disable compositing button there. Enable it!
If the desktop complains, then go to the Advanced tab and click on the ‘Disable functionality test’ option.
You can Enable all Desktop Effects too.
Switch to the Advanced tab.
Compositing type: OpenGL

You should be good to go!