I made the switch over a year ago from 1080 to 1440. I game on a 32" Samsung 2560x1440 and I love it.
I have a GTX 980 currently so I have plenty of power to push the pixels.
I tested several settings recently in Far Cry 4 and noticed that I was able to max out all settings and still get 60+fps with AA turned off.
With it on I was getting 30 to 45fps. At 1440 I can't tell much of a difference with AA on.
I've read that at 4k "AA" is useless.
I enjoy it and after having it for a year+, there is no way I'd go back.