I can confirm that the 2012 can also drive 2560x1440 through the HDMI. I had to use SwitchResX. The Pixel clock is still limited to 162Mhz. In SwitchResX I was able to drive my Dell U2711 at 40hz when I used CVT-RB as the custom settings method. 40hz isn't ideal of course but is plenty as I am using this as a secondary monitor, the primary is a 30". I have been able to drive the U2711 using HDMI or the HDMI to single link DVI dongle. For some reason the colors look washed out using the HDMI so I'm going to stick with DVI.