Yes I do actually, since I only have two usb ports on my Air. I've connected a powered usb hub on one usb port. And in that hub, I've connected my printer, 2 external drives, keyboard and usb-thernet adapter.
Offcourse, not all of these devices are used all the time, just the keyboard and ethernet adapter. The printer is on standby I guess.
From my experience, I've noticed kernel task goes mental when watching youtube. Wether it's with Safari or Firefox. But I've almost stopped watching youtube on Safari since it lags every 10 sec, even on 720p...
But my MacBook also froze on a screensaver. I wasn't in my room for a while, the Air when to the screensaver after a few minutes, I got back it was frozen on the screensaver and the fan was blowing like crazy...
So I really can't pinpoint the problem
Theres also a problem with the screensaver, sometimes it works and sometimes it doesn't... It's like they reversed something, the screensaver will start while youtube is open (but not playing) but will almost never start when I'm not even using my laptop and it's just on the desktop.
I'm really not liking all the OSX problems, I believe Apple is too focused on the iPad and iPhone, that they're neglecting the Mac.
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I have that as well, very weird. It happens when you quickly hoover over something.