After breaking in the E8000 for around 185 hours, I decided that was enough and put in the CNET settings and watched Yellow Submarine tonight. Right away, within 5 minutes, I saw the screen turn off when the screen went black for a moment. Right before the main title sequence starts with the Yellow Submarine song, the screen went to black briefly and the screen instantly turned off, then flickered quickly for a second or two until it came back on.
The same thing happened again at the end, just after the "All Together Now" credit sequence finished, and went to black. Again, the screen instantly turned off, then flickered wildly for a couple seconds until it came back on again. My girlfriend and I noticed it both times and it is very disruptive and annoying. The ST50 never behaved like that. The weird thing is I never saw this tv do that with all the hours of break-in I did. The first time I sat down to watch a movie tonight with the CNET settings put in and it happened.
I have the brightness set at 46 because a poster in the thread here mentioned that setting the brightness from 45 to 46 eliminates the screen turning off during black screens, but that did not seem to be the case for me. I played the last scene over again with the brightness at 47 and the same thing happened.
I called Samsung and reported the issue, and mentioned that even CNET talked about it in their review of the set, and that it is mentioned in the forums as well. He seemed to understand what it was doing and said he will escalate it and hopefully it would get fixed in the next firmware update, but I'm pretty sure that's just something they are supposed to say. He also said I could fill out the online form on their website and report it as well. I urge others to also call Samsung and report this issue if they have noticed it. It is the only way they will address the issue.
I haven't watched enough tv yet with the CNET settings to get a good idea of how it looks yet, but I do notice that the blacks don't seem nearly as good as the ST50. I was hoping they would be pretty close, but so far I'm not blown away by the blacks on this set like I was on the ST50. I'll watch some Battlestar Galactica tomorrow and hopefully with some nice space scenes I'll get a better idea of just how deep the blacks can get.
I will say the screen seems plenty bright. The scene with the Nowhere Man song had tons of white and it looked quite bright to me. The colors look very nice so far. But this problem with the screen turning off has me very concerned. It is very jarring and ruins the scene.
EDIT: I was just watching some of "Tree of Life" on Cinemax and saw the screen turn off late in the film when a space scene fades to black. The screen turned off for a couple seconds before turning back on again. I don't know if it was doing it during break-in and I haven't noticed it before now, since for the most part I wasn't paying much attention, or if somehow CNET's settings make it more noticeable or actually trigger it happening. All I know is this is awful and I can't believe Samsung would think this is a good thing. I asked in this thread before I bought this tv if this would be a problem and the response was "no". Well I've nooticed it several times tonight already and it's a total deal-breaker for me if this doesn't get fixed. Unfortunately I've got less than 3 weeks to return this set now and I'm sure even if Samsung will fix this it will take longer than that for the fix to get released, so now I have to decide if this is something I can live with. I think the image is excellent overall other than the weaker black levels, but this screen turning off issue is going to be something I see alot I think, and I hate it.
EDIT: It did it again several times during the end credits sequence of Tree Of Life, in between credits. What was Samsung thinking?