There's been quite a few of similar threads, it will differ per person.
2560x1440 is great for getting work done, especially with Window 7 Aero Snap it's nice to have windows side by side and it can really boost productivity. Very nice viewing angles and excellent colours on the Hazro.
120Hz is great for gaming but the resolution isn't any higher than that found on 21.5" screens (or even 15.6" laptops!).
I personally have a Hazro as I just love having tons of workspace and I can't stand how huge everything looks on a 27" 1920x1080 screen. Makes text on websites look so big it's like its made for people with bad eyesight, during gaming that isn't really a problem however.