It's confirmed that the Galaxy Tab is using an LCD display, and not an AMOLED.
As for the LG prototype and such, it's pretty exciting, but it should go without saying that sales will be infinitesimal at those prices, which aligns well with production capacity.
Before we get excited about a 50-inch display, ask yourself if you're willing to pay $15,000 for one in 2012. Because that's pretty much what you'd be looking at. A good 50-inch LCD or plasma is already well under 10% of that.
OLED is supposed to be cheaper than existing stuff in some theoretical future. But that future really feels closer to 10 years away. And I say that in light of the LG announcement.
There is no difference in HDMI cables. If you can see the picture without visible dropouts or sparklies, the cable is working at 100%. No other cable will display a better version of that picture. You're simply wrong if you think there is a better digital cable than one that is already working.