I cant comment on the 60hz to 120hz because my eyes cant tell a difference. I think the response time is 5ms on the one I bought below.
I just bought the Yamasaki Catleap 27" LED 2560x1440. I absolutely love it! Ive played battlefield 3 on it but I suck but the graphics were incredible. Ive been playing Halo 2 ever since and its phenomenal for me. It brings me back to my glory days, just way more pixels :-)
I came from a 22" Samsung ToC Eyefinity Setup and will never go back after this monitor.
Got mine on ebay from seller green-sum for 289.99.