I highly disagree!
Bought a 42 philips tv as a PC "monitor" back in 2010 (not even led lol), and had 0 regrets of doing so for 7 years - its still working without any problems. except of small parts of "dying" crystals (they appeared ~1.5 years ago) or something like that, on the top edge of a screen (they look like a bit darkened parts), but after 7 years of using tv every single day, for 10-15 hours each day, its no wonder.
I have never experienced any input lags. Maybe i was just lucky and bought a good model, because i didn't even hear about such problems on tvs before buying.
For entertainment purposes (gaming/videos), TV is a superior because of its size. Flying on a jet in battlefield 3 on 42 screen was breathtaking (for first few weeks of flying i even felt dizzy all the time) and still is. Immersion is huge!
For watching videos its even better - im using SmoothVideo Project for 24->60fps increase, and sharpening filter in my videoplayer, so the picture is so amazing (even for such old tv as mine - on modern LED tvs with increased HZ, brightness, and build-in fps increase things it should be much better).
I highly reccomend to ensure about TV resolution on PC connection before buying! Some tvs (as mine) have 1080p on video signal (like TV/PS3-4/Xbox), BUT maximum PC resolution (on PC with HDMI) is 1680x1050 (1080p is here, but its blurry). I dont know how to explain this, but thats what i faced and wasnt able to fix for years - maybe this problem doesnt even exist in modern TVs, but you'd better to check it before buying!
Also i've noticed that i need "bigger" fps to feel comfort - for my TV comfort zone is ~52-60 fps (the bigger the better obviously), everything less than 50 is not so good looking, and less than 40 is very uncomfortable for my eyes. I dont know how to explain this, maybe its somehow connected with fps-hz, or thats a simply "feature" of all tvs, or maybe just old ones. On average monitor i started to notice influence of bad fps only lower 40-45 fps.
PS Sorry for bad english.