As we already blogged some time ago, we had severe overheating issues and frequent kernel panics with our early 2011 models of the MacBook Pro Core-i7 quad. Still, after the updates there are crashes from time to time - the early 2011 models are far away from being stable machines to use for serious work.
After days of trying to figure out what is really the issue, we found that most of the times device drivers or other third party apps are mostly causing the crashes - but also CPU-intensive apps such as games sometimes bring the system down. Solution? Yes, there is one: change your system to a 32bit Kernel.
1) The bootup way (temporary solution, great for testing)
If you just want to test if changing to 32bit changes anything, you can reboot your mac and hold down the "3" and "2" keys as soon as you hit the power button. This boots up your Apple in 32bit mode temporarily. If the system
2) The Terminal Way (see the Apple Support Document for more information)
sudo systemsetup -setkernelbootarchitecture i386
if you need to change your system back to normal for any case, you can enter the following command into Terminal.app:
sudo systemsetup -setkernelbootarchitecture x86_64
Just to make it clear: your applications will still run in 64bit mode, you can make sure this is the case by hitting cmd+i on the application icon and see if "Open in 32-bit mode" is checked. See this article from simplehelp with details and images on 32-bit mode. So why should I care then, you might ask: since drivers and 3rd party apps and extensions that are loaded on startup are most of the time the issue with system freezes and hangs, changing to a 32bit kernel did the trick for us and now we have a stable 2011 MBP quad-core system.
[UPDATE] 10.6.8 seems to work with 64bit kernel much more stable than 10.6.7. Still, to be on the safe side we are using the 32bit kernel and had no freezes yet.