After I wrote a bit about AIGLX and new NVIDIAS drivers I realized that it is not entirely clear what will happen with KDE in this case: at the moment there are technically two window managers available which are also compositing window managers taking advantage of the new features around these days: Metacity and Compiz. Metacity was and is mainly developd by Red Hat for their AIGLX project, while compiz was and is developed by Novell for their Xgl project. The base for both was the GNOME desktop environment.
KDE has its own window manager which is capable of some effects at least through the xcomposite extension provided by X for now quite some time. However, I never heard that someone is actually working on the KDE window manager to bring it composition abilities like compiz has them: to make fancy effects for the task preview, the minimization effect, or to have a flexible plugin architecture to add such effects as a plugin provided by others (I think at least the compiz-fork beryl has it).
But there are some news in this field at least: in this weeks commit digest there were some changes listed which make KDE able to use compiz as a window manager officially – without any of the dirty hacks which are around atm. Together with the compiz fork beryl, which does not depend on GNOME anymore, this could be a real alternative. I hope that the akademy conference will bring some more information about how KDE4 will handle these fancy things.
Update
Narishma reminded me with a comment that there was once a basic composite support for kwin introduced. But there haven’t happened anything in the svn repository for the last 2 months, so that does not really count. We have to wait for akademy reports.
/home/liquidat 
Hmmm my browser seems to have eaten half the formating of my message so… trying one more time.
“However, I never heard that someone is actually working on the KDE window manager to bring it composition abilities like compiz has them: to make fancy effects for the task preview, the minimization effect, or to have a flexible plugin architecture to add such effects as a plugin provided by others (I think at least the compiz-fork beryl has it).”
You might have missed (or forgot) that Lubos Lunak did some work on kwin to support such effects back during the KDE 4 Core meeting. More info on his blog.
Yeah i hope to see something.
But the Development is a bit at sleep. I asked sometimes on the #kde channel wo implemented the Composite features in kwin because they are not really good to work with.
Perhaps somebody should bring this topic back to life.
@Narishma: you’re right, I just forgot about that. But I checked the svn repository and there was no improvement since the first introduction of the new code.
But thanks for the comment and feed back.
@Russel: That’s one of the reasons I would love to read more information about how akademy went: I hope that this topic was raised there. I’m not a KDE developer and do not have any influence on the KDE community so I can hardly raise the topic there