i can't comment on the 'judder', that's something i truly don't see. i absolutely hate the way frame interpolation looks though.
it's good to hear the picture quality has gotten much better over the years.
input lag isn't really directly related to 'smart' features. it's more a matter of processing, and typically higher end tv's have both smart features and a lot of processing. but that's neither here nor there, the important thing is that the s60 has tested with good input lag numbers. my f8500 has nearly double the input lag(when not in game or pc mode) and i still find playing games like COD 'normal'. playing kinect games was pretty tough though. there's definitely a large amount of personal sensitivity when it comes to input lag. when i went from CRT to plasma, i didn't notice anything. and when i went from 'simple plasma' to the f8500, i didn't notice anything either, except for the kinect stuff.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1018AH, 5.1 audio
Sources: HTPC(Mediabrowser), PS3, XBOX360, Wii, Sony DVP-CX995V
Control: Harmony One