Also make sure your display isn't trying to interfere with its own scaling.
This is what 2560x1080 should look like on a 2560x1440 screen. Top is 16:9, bottom is 21:9. Notice that nothing is stretched or compressed (yes, things are smaller and composed of less pixels, but 3414x1440 displays don't exist). Things also get smaller in any game that has an adjustable FOV, so it's the same difference.
The issue that causes confusion in this thread is everyone is 'oh noes 21:9 chops the top and bottom of my 27" display off,' when in actuality a 29" 21:9 display should be compared to extending a 23" 1080p display 6 inches wider. Because physically, that's exactly what it is.
That said, I am all for more vertical lines, and if a 3414x1440 display existed I don't think many people would have an issue with that.Edited by zinfinion - 3/29/13 at 7:10pm