A couple updates after a year of ownership of a UN55EH6070. I last posted to this thread about a year ago.
The audio sync problem with the new firmware: It can't be fixed. Never had an audio sync problem until I updated to the latest firmware which claimed to "fix HDMI audio sync problems" and improve picture quality. Well my picture quality does look better, see below. But as soon as I installed the updated firmware, I noticed random and frequent severe audio sync problems via HDMI connection after changing channels or start/stopping/skipping content on Dish Network VIP 722k DVR or Panasonic Blue Ray player over HDMI. I tried everything, bypassing the AV receiver, service settings etc. No accessible settings can fix the severe sync problem. Deep searches, including earlier comments on this thread, seem to indicate an un-fixable "lip sync" defect on this model. The work around is to turn the TV off and on again to reset the audio. Not too bad at first glance, but it happens 2 or 3 times when channel surfing over an hour. This is poor quality and disappointing result of a Samsung firmware update. I'll be dropping stars on my #1 rated Amazon review shortly. Not that it matters since the model has since been replaced.
One positive result with the new firmware is improved picture quality. It looked different and good after firmware update but something was not quite right with contrast or brightness. While troubleshooting the audio sync problem I decided to download a chess calibration pattern from other threads in this forum and run the advanced service menu HDMI calibration. With that and and another calibration from the Disney WOW Blue Ray, I can say that my picture quality is quite clearly the best it has ever been. Something in the new firmware improved depth or dynamic range or perhaps contrast management. Calibrating lead me to bring Color setting down to 39 and brightness to 44 to avoid edge viewing angle black wash, with backlight set to 20. The picture is noticeably more rich. Outstanding picture quality in fact. Except for the poor viewing angle performance (compared to our old Vizio in the bedroom). I use an AV receiver for movie and serious sports viewing which eliminates the audio sync issue over TV speaker. However, for daily family/kid viewing, that audio sync issue really sucks. It is sad that it cannot be fixed.
Avoid this model unless you can work around the audio sync issues via AV receiver. UN55EH6070 TH01 panel type. I did expect better firmware and support from Samsung. I will only buy Samsung again if OLED/4K price points stay below the competition in 2015 or 2016.