First - one important thing. Blur effect works for some of KDE elements, like Plasma widgets. Everything under them are blurred, as in Windows Aero. The wallpaper under taskbar seems blurred too. But one thing not blurred is terminal background, which makes its transparency useless, because text is hardly readable, when there's another clear readable text under the console window.
In GNOME it works. Both with guake and yakuake. The interesting thing is I've tried to use fusion-icon to switch window manager to compiz. My compiz is incompatible with KDE window decorator, but I only wanted to see if the blur works. It doesn't work even with compiz window manager instead of kwin. But interesting finding here is KDE worked way faster with compiz. I got more FPS, but well... no decorations, so unusable anyway. Besides compiz is very unstable and buggy, I think kwin is more mature project and if I'm to use KDE, kwin is the way to go. But blur problem - it's not kwin. It's broken on compiz too. (It works good in GNOME).
I've tried turning direct rendering off. It didn't help with blur. I'm not sure if it helped for performance. No. No difference.
What is raster graphicssystem? Is it something I can install? I couldn't find package named raster*.
X 1.10 - right, same for me. Tested on Ubuntu. Is there any workaround for this?
I have a specific reason for using catalyst, it's tear-free feature. I couldn't make movie players to play video without major tearing until I've checked option "tear free" in catalyst. But I only tested this in GNOME, maybe in KDE standard vsync options will work as expected. In GNOME they were randomly ignored. I've changed a compiz option. Cool, no tearing. Reboot - tearing again. Different settings - no joy. Worekd once, doesn't work again. A few reboots and suddenly it starts to work. This one was a major PITA for me. So ever since - I use fglrx and "tear free" option. This just works (but also use some of my video memory, which is not so good).
Ok, fglrx always sucked, so... How do I switch to open? Just uninstall fglrx packages? Should I install something else instead? Do I have to manualy modify xorg.conf?
How to downgrade xserver? I've tried downgrading things on Ubuntu, it NEVER worked and I always ended up formatting and installing everything from the start. If there is a safe way, I'll definitely want to try it.
Reinstalling is not an option. I don't have enough time to configure all of my stuff again and rediscover all LMDE hacks applied
Wait, how did you disable direct rendering? In KDE settings, or somewhere else?