The only reason you want to run a monitor at multiples of 24 is to display 24 fps content like blu-ray films without judder. This would be noticeable on camera pans as a slight "hitch" every few seconds in the motion.
Otherwise pick the refresh rate that works for you. 120 hz would only be useful if your video card can drive games at close to this speed. At 120hz you could display up to 120fps in gaming and avoid obvious tearing. At 2560x1440 this is not so much of a problem. Otherwise the only real advantage is a smoother mouse experience and possibly less motion blur during scrolling.
I just received mine yesterday and I'm ecstatic with this purchase. After disappointments with the Achieva Shimian 27" and the Overlord Tempest 27" (no overdrive), this monitor has been a beyond pleasant surprise.
I bought the "QniX Matt(e) pixel perfect" version from dream-seller for $307.00 U.S./$328 Canadian plus $52.88 taxes and duties (supporting my govt for doing nothing). It is indeed pixel perfect and back-light bleed is non-existent. I have perused it over and over again looking for flaws and it doesn't have any. Uniformity on black and whites is quite solid, and whites show no yellowing in corners or sides.
Right now I'm running it at 96hz and am happy that I can drive it with my SLi Titan setup at this refresh rate in most games.
Very impressed and relieved so far. Now to calibrate via BasicColor and use Color Profile Keeper to make this ICM profile persistent in games and enjoy. The whites are a tiny bit cold and the gamma is very slightly off but otherwise this monitor has drastically exceeded my expectations.
Thank you for the reply, I have bought 3 non pixel perfect ones, and so far the one that arrived seems good to me.
I have to issues though. When I overclock the refresh rate, my video card will not do 32bit color scheme. If I put it to 32 bits, it knocks it out of the over driven refresh rate back to 60Hz.
Second thing is, when I overclock the refresh rate, and this may be due to the drop to 16bit color scheme, things seems to get darker and more contrast. Not in a bad way ,but just different. Is that normal? Do I need a separate color profile for the 120Hz refresh rate?