I've been using a 47in LG lcd for about 6 months now,I was going to get a 55 in but found it was too big for the distance I sit from it and this might have caused an issue if I ever get trackIR.
I have a clone setup with a 24 in widescreen monitor and checked to see if there was any input lag as mentioned and if there is I couldnt notice it.
I use the vga input as my vidcard doesnt have hdmi. Be advised even if the screen says it's 120hz/240hz it will only run at 60 hz in pc mode,mine happens to be 3d but I only got it because the $$$$ was right and a non 3d screen with same specs was actually more money at the time.
If you really interested in trying this,go to a small AV store and ask them to plug a pc into the screen and watch it yourself,most the bigbox stores wont do this as it's"too much trouble".
You wont get the fine resolution of a PC monitor,limited to 1920x1080 but your pixel size will be larger and you'll see "enemy dots" long before most others will.This has been a huge help to me with my poor eyesight.
YMMV.
PS: I can tell what plane is what at more than 2K out now and even what direction it's going,couldnt do this with the 24 inch screen at any resolution.