Flat screen HD tv's are for exactly that HD tv as most tv channels broadcast bandwidths of 576i or did so when broadcast on a panel of 1080p the tv has to fill in all the extra pixels thats why some HD tv's look awful on some programmes however feed it an HD source like blu-ray or Sky/Virgin or even freeview HD and you should get a cracking picture.When looking for a new tv here's my understanding of all the tv techs-
Plasma-
Pro's-Great motion handling
-Generally better contrast(blacks)
-Great viewing angles
-colour
Cons-
-Use more power
-Screen can be reflective in daylight
-Only come in big sizes 37"-65"
LCD-
Pro's-more screen size choice
-Brighter in the day
-lower power consumption
cons-Contrast(blacks)tend to look grey in the dark on lower end models
-Viewing angle can be poor
-Can be poor at fast motion handling sports/movies
LED-
Pro's-low power consumption
-really thin and light
-good colours
Cons-
Viewing angle can be poor
contrast(blacks)can look grey in the dark
can be poor when handling fast motion scenes sport/movies
This is what I understand to be the basic pro's and cons of each tv tech when looking for a new tv,however im no expert and don't judge a tv by how it looks in a show room as they pump up the brightness tend to feed it an HD source and those show room lights don't reflect general home lighting.