That's actually my blog linked to there.
Yes, I'm seeing the best performance by using the method that Martin Gräßlin showed me (Alt+F3 -> More Actions -> Special Window Settigns -> Appearance & Fixes and enable block compositing/force/yes). The next best was my original idea (suspend for full-screen windows), and worst by doing nothing. The difference is not *huge*, but using Martin's method, I'm hovering around 300fps @1920*1080 in CS:Source and between 45-80 in Serious Sam 3 (I get more in Survival mode, less in Campaign mode, I guess there is more going on). This is on a 3770 @4.1GHz w/ an Nvidia 560Ti running the 313 drivers in Kubuntu 13.04.
Also, in Serious Sam (I need to blog this, if for no other reason so I'll remember it, that's generally why I blog), you can issue the following commands to enable multi-core rendering (it only is using one CPU thread by default for me):
I've read that even on an 8 thread i7 (or AMD FX) you shouldn't go over 4 on the iMaxThreads setting as it'll flood the driver and result in lower performance. I would guess either 2-3 for a 4 thread i5 or AMD would be optimal.
Also, just to note, I've tried Unity and Xfce as well (under 13.04), and the performance isn't really all that different in real-world gameplay. I'm sure true benchmark runs might show some, but I play games on my machine, not run benchmarks most of the time. Even in KDE is slightly less performing (and I can't really see that myself), is the most productive DE for me for everything else, so I'm happy w/ Martins little Window Rule trick.