The U2711 and these monitors have quite a few difference:
1) The Dell has a 10 bit panel capable of displaying 1.07 billion colours. (though no one uses it due to hardware and software limitations)
2) Able to cover Adobe RGB (For colour correction to prints)
3) Many many inputs. DVIx2 (with HDCP), D-sub, HDMI, DisplayPort, Component, Composite.
4) Has inbuilt scaler, hence devices such as PS3 can run at 1080P and the monitor will upscale it to 1440P. However, the scaler introduce quite a bit of input lag.
5) Built in USB hub and 8 in 1 card reader.
6) Factory calibrated(my 2 U2711s are pretty close in colour)
7) The Dell uses CCFL back light, which consumes much more power compared to the W-LED back light of the cheaper monitors.
8) Antiglare cloating is a little strong.
This is awesomely cheap and super value for money, if you got a flawless panel. I got both my Dells at $719 and maybe might get a 3rd one when a new model comes out and place it in the centre.
Regarding gaming on a 2560x1440 monitor, my Ati Radeon HD 5870 is able to drive one monitor satisfactorily. Eyefinity on 2 monitors is a bad idea thou.
Cheers.