I'm sorry, it's my mistake it's not glxgears, its

glxinfo | grep direct

If the answer is "yes" and you see chopping screensavers in the first run of the X server, try rebooting.

To go back to your previous settings, just run as root SaX2. This will automatically select the "intel" driver. Test the configuration and if all is well, save it. You should be back to where you were.