45 FPS is not enough for me, like I say over 100 is a lot smootherYeah DX11 is actually better optimized than both DX9 and DX10, judging from the various benches I've read if only by a couple FPS.
With a quad core and a GTX 480 it should be maxed out easy though, my GTX 460 can run it fine at 1680 x 1050 with high details, HBAO and AA at above 45 FPS on average.
You will not notice the difference above 60 fps on a 60Hz monitor, as the monitor will only be able to refresh 60 times a second.
It is impossible to notice the difference, unless you have a higher refresh rate.
Like I said people will argue this all the time, there is two sides of this story but I really don't won't to argue who is right or wrong, all I can say is I do notice the difference.