Well... it's anecdotal of course, but I just got a really nice 3440x1440 34" wide monitor, one of those Korean budget ones, and it's very nice. I haven't played a lot of different games, but World of Tanks has worked fairly well. I did have to disable shadows, I dunno why, but I did. Shadows under tanks is pretty pointless anyway, so no loss. Looks great, big improvement over my old 27" 1080p. My monitor is 3MS and 144 hz, although I run it at 100hz for compatibility, which seems to make it less buggy.
By the way, my graphics card is nothing special and it has run fast all the time, although I keep the rez at medium setting. I really just care about killing tanks efficiently.