This has been a long problem with Compiz that NVIDIA never fixed, intermittent performance problems such as hick ups; the problem is easily reproducible moving the cursor while opening programs such as Firefox or Evolution. Until Compiz 0.3.4 this bug was fixed setting the __GL_YIELD environment variable to "NOTHING" in Compiz environment. Since Compiz 0.3.6 setting the __GL_YIELD environment variable to "NOTHING" is not enough, but launching Compiz WITHOUT "--unredirect-rendering" is also needed to fix this. So whats the problem using direct-rendering? using direct-rendering triggers the NVIDIA vterm switching bug, that makes the screen keep black on vterm switching. If one clicks at the black screen, a hard reboot is needed; the only solution is to kill X and start it again. Also, for some people like me, using --indirect-rendering gives better performance than using direct rendering. I hope someone fix this before Compiz 0.4.x is out, and make it work at least as it worked in Compiz 0.3.4. Thanks in advance.