It appears to be something about the small CPU they use. Folk that are used to responsive PCs, tablets and phones are comparing user experiences to HDTVs.
I'm not saying that's a bad thing.
When I use my Samsung to check the TV Guide, and I try to scroll up or down it tends to freeze for a little while before getting to the next click of either up or down.
It only takes a few seconds and then continues and can still happen a gain.
It happens sometime right away and at others after maybe 8 click while scrolling.
I have a UA46D7000
Is this normal as my friend purchased UA55D7000 and it also happens to him.