LCD/Plasma Pixelation
This is largely due to the stupidly huge screen sizes being offered today. Remember, the video produced is only in (at least here in Australia) 720 x 576 for Standard Definition, I think "PAL."
If you try to stretch that across a 60" TV, you're not going to get excellent results.
Then there is the cheapness in broadcasts. Its so surprising, they tout how much better picture quality you're (supposed) to get - but they uber compress their video signals, so where Full-HD (1280 x 1080?) is supposed by at a high Mbit rate (e.g. 20), it is half or even just a quarter of that, to save transmission costs and storage space.
The result: Garbled, pixelated TV as a result of heavy MPEG compression rates and pictures being stretched to fit huge tv sizes.
Given the choice, I would NEVER NEVER NEVER buy a Plasma TV again. We currently have a 2007 Panasonic Viera model, 42" size. Its generally a nice picture on properly made broadcasts (usually from SBS/ABC), but the amount of heat it generates and electricity it WASTES is horrid. Somewhere around 400-500w - during the course of the evening, there goes about $3 worth of electricity at our rates.
Of course, the added heat causes the A/C to work harder in Summer, and being in-efficient as it is, it drives up our cooling costs even more.