High refresh rate is quite noticeable when playing, but far harder to tell when you are only watching. You also need high FPS to fully take advantage of the high refresh rate. The biggest thing I notice with 120hz vs 60hz, is with the FPS to match, a games view feels like it is connected to my mouse, rather than feeling a tiny bit of lag, it is smooth. For myself, personally, I used to get sick playing FPS games until I upgraded, and got my FPS over 80 (similar to motion sickness).
Last, the difference between 144hz and 120hz with Lightboost is supposed to be bigger than the difference between 60hz and 144hz. Lightboost removes motion blur, so you see all the images clearly, rather than blurry motion. http://www.blurbusters.com/zero-motion-blur/lightboost/