Is this something you wouldn't notice if you hadn't seen any different? I still game on a 24" 1200p monitor I bought in January of 2008. I am fairly successful in Counterstrike, so I know it doesn't hurt my game play.
I'm not sure if you're directing this question to me, but here goes:
Yes, you notice a marked difference, or I wouldn't have enthused about it so much.
The motion blur and judder artefacts are very noticeable even without comparing to anything else. My previous monitor was a good quality Iiyama 26" 1920x1200 monitor and it's
waay better than that. Here's how the animation/movement quality increases as you go up the improvement scale.
60Hz - lots of motion smear and poorly defined edges. Judder can be highly visible too, depending on speed etc. Lot's of lag (this is relative, though). My Asus 144Hz monitor is no better than any other monitor when run at 60Hz.
120Hz - much smoother motion. Still lots of motion blur, but edges don't break up so easily. Dropped frames from the graphics card don't look so bad. No noticeable lag.
144Hz - incrementally smoother motion and visibly less blurring, but it's still significantly there. No noticeable lag.
120Hz LightBoost mode - fantastic performance and gaming Utopia is achieved!
Everything was just so vivid and clear on the Asus that it honestly
did make my jaw drop - this hasn't happened to me ever since I can remember. You can enemies moving around quickly with great clarity and all the special effects really come to life, such as explosions. Turning LightBoost off on the Asus made it much like the LG. Basically, strobing the backlight makes all the difference and it's a wonder that this simple and obvious technique hadn't been brought to market years ago as a standard feature of "gaming grade" LCD monitors, independently of any manufacturer. The difference is simply stunning and makes an LCD better for gaming than a CRT, because it has all the same motion clarity while retaining its inherently pin-sharp picture. No noticeable lag - it makes no difference to it either way.
I did a simultaneous comparison (clone mode on the two DVI outputs) at 120Hz between my Asus monitor using LightBoost and the LG without LightBoost as it's not supported and the difference was very noticeable. Basically the LG looked like crap next to it. Turning LightBoost off on the Asus made it much like the LG.