true 120hz are worth it but so is a high res IPS monitor its really up to what you use your PC for. Also 120hz really doesnt do anything for tvs at all its just a marketing ploy.
As a person who has programmed and tested 120hz tvs before I'd have to disagree. True 120hz tvs with motion interpolation do drastic things to tvs, anyone could spot it instantly pretty much, and no its not all good either, lots of things like movies and tv series start to look excessively... fake, which is why I think a lot of TVs now come with most of the 120hz features by default off.
For a brief info:
First there is fake and true 120hz. Fake 120hz, the TV is incapable of updating the screen with new images at 120hz, but it can display at 120hz, basically it'll display the same image twice every time, with the way most TV technologies work this does have an improvement, but only very slight and you probably won't notice it most of the time. True 120hz is capable of updating new images at 120hz, but of course pretty much all content is at most 60hz or less so there's not much improvement there either.
The real applications are 3D and Motion Interpolation. With motion interpolation your TV uses algorithms to make things 120hz. You can see this affect almost instantly, its kind of hard to explain but lots of things just look fake, the mastering for the films and most tv series seem to be specifically designed for lower frame rates so upping it to 120hz makes it seem less like your watching the film and more like your watching a documentary showing a live filming kind of thing. For other stuff like sports and what not though, the motion interpolation looks great.
3D is pretty obvious, you get 120hz, you can put on those shutter glasses and see in 3d. Though it may seem like marketing, but you should actually get a 240Hz tv, even a fake 240Hz tv, if your going for 3D. The shutter glasses work by blocking 1 eye and then showing each frame as a sequence of frames for Left and Right eye, so your frame rate is already cut in half to 60, then the effect of only seeing in 1 eye at a time seems to halve the frame rate again in your brain so it seems like your watching a 120hz 3d film at 30hz which can definitely cause tiredness and strain. 240hz at least counteracts the brain part so it seems more smooth and less tiring.
Ehh so tl:dr: 120Hz TVs only help if what your watching is at 120Hz, having the TV upconvert to 120Hz works but it can make it look fake.