UPDATE November 24: I'm relieved to report that the touchscreen issues described below appears to have been resolved by a firmware update released on Sony's tech support site.
Kudos to TabletPCReview forum poster Miles Wolf, who first spotted the fix.
I installed it yesterday morning from Sony's Japanese tech support site and haven't experienced the problem since. The bios update is now available on Sony's US eSupport site.
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UPDATE: Additional testing of the Flip has surfaced a much more serious issue than pen pressure or fan noise. I must recommend that you avoid the device until the issue is corrected. See this post for more information: http://surfaceproartist.com/blog/2013/11/14/the-real-dealbreaker-for-sony-vaio-flip-15a-frequent-loss-of-pen-touch-control
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Buried deep in most discussions of the new Sony VAIO Flip series is mention of the loud fan noise. But I believe this issue must be surfaced immediately because it might be the device's fatal flaw. In other VAIO models, fan speed can be adjusted in Sony's control panel, but that is not an option with the Flips.
Like most pc's, fans whir up at startup and usually quiet down. But what's unusual about the Flip is that the fans will come on even when the device is idle. And if you're watching a video or working with graphics, they whir continuously. After a 30-minute session in a quiet room last night, I was afraid it would bore a hole in my skull.
This video demonstrates the startup fan noise, but it's pretty much what you can expect to hear throughout your workday with the convertible. This video was shot in a noisy environment, right above a loud mini tower pc. Turn up the audio to hear the dramatic difference once the VAIO powers on.
It's possible that this issue may be addressed in a firmware update, but I haven't seen any official word from Sony.