Just to add on...
"The difference is there but not as big as some people make it out to be."
I will say this can be true. I think some people can go a little overboard on how BIG of a difference it is and how it's soo "life changing" or as dramatic as "night and day". That being said. Do I regret buying 120hz? No, no way. Was it worth it? 100% yes...completely. 120hz is most noticeable in fast pace gaming like shooter or racers compared to my 60hz IPS... (might not be the case for other games..not sure, only been playing BF3).
I will say that 120hz made my PC/graphic card "feel" more powerful....removing the 60fps cap and moving the limit to 120fps IS noticeable and more enjoyable (even tho i only get 65 - 85 fps in BF3). I can actually get more value out of my hardware (gfx card) ...i can actually SEE the difference (at least compared to my 60hz IPS). In the end, the cost was worth it to me based on the improved game play. Not sure if it will be for you or anyone else.
It is not like "OMG THIS IS THE BEST THING EVER..MUST HAVE UPGRADE. I CAN NEVER USE 60HZ AGAIN!! HOW DID I EVER USE 60HZ!!"...its not like you are going from 20fps to 60fps...but more like "DAMN THIS IS NICE, SO SMOOTH - I LOVE IT!".
So in short...100% worth it. 120hz (or IPS for non-gamers) and SSDs should be standard upgrades for enthusiasts with cash to spare..imho. Best two new upgrades in the current pc market.
And just FYI - Would I ever buy a 60hz again for gaming? If I have a choice..No, probably not...especially for fast pace gaming...Can I still game on 60hz? Yes, I'd game on it just fine...but I would rather be on 120hz..if I have the hardware for it. I won't cry if I had to play on 60hz...
PS: My comparison is mostly comparing my 60hz IPS vs my 120hz TN. I am sure there are faster response 60hz TN panels...where the difference is even less so...but overall...I think it would still be worth it...especially, if you graphic card can push 75+ fps.