120hz (as a 1440p owner) for fps 27" is just too much screen.
Too much screen?
I love 27" for gaming, and not having enough room for 2 x 27" went IPS over 120Hz.
Just find single 1080p too restrictive when not gaming.

I find i get distracted looking around the expanse of 27" goodness. I'd rather a 1080p 24" 120hz monitor. Plus it's easier to push good graphics to!
2560x1440
But if this is for gaming you would need a couple of 6990 to play with filters @ 60 FPS.
no you wouldn't?
. To be honest once you have been bitten by the high res, ips colours and no need to use AA I don't think you can go back to 120hz? But it's up to you?Yes you would.
I play Battlefield 3 using 1080p, Ultra and 2xAA. With a couple of 6870, and sometimes my FPS still goes under 60.
BTW, the 6870 Crossfire is about 10% weaker then a single 6990.
Dood 1440p, bf3 and a good Gpu =. To be honest once you have been bitten by the high res, ips colours and no need to use AA I don't think you can go back to 120hz? But it's up to you?