I have periodic bouts of kernel_task going crazy for no apparent reason and ramping up to 500-600%, today it even hit 1800% for a bit. The computer slows down to a crawl in these cases and it's unusable.Sometimes it will do it even after a reboot, until left alone for a while, presumably finishing whatever it was doing. This is on a new Mac Book Air with 8gb RAM. I've had the same issue on a 2011 Mac Book Pro with 16gb of RAM too and it kept getting so hot that it fried the graphics card (which is bad on those Mac Book Pros, anyway). Anyone with a reasonable resolution? I see that people go as far as disabling kernel_task for their Mac model, but this seems likely to cause its own issues. As a side rant, I am noticing a host of issues with the last two Mac OS versions. OS10 also has a problem with Mail bleeding resources at times, requiring a restart of the app. I am sort of getting fed up.