Ive been using this: http://www.mwave.com.au/product/aoc-u3477pqu-ips-34-3440-x-1440-5ms-displayport-led-monitor-with-speaker-ab56427 for a while now. Originally I was using a 22" 1650 x 1050 and I've found a few pros and cons with it.
Good things - Its much more immersive, very good colours, the higher PPI helped a lot in DCS and overall a huge upgrade from my old monitor.
Bad things - Its ruddy expensive, there's a fair few games without support for this type of monitor and its not unusual to have to edit INI settings in order to make certain games work. Unfortunately other games flat out won't run anything from Ubisoft and a few other random titles are forced 16 : 9, most cut scenes in games will be locked at 16 : 9, Its 2.8 times more difficult to drive than full HD. I use an r9 290 and am able to max most games at this resolution but I would consider that the minimum requirement for playing modern games at high setting on this monitor.
I love it and wouldn't go back the only thing I'd consider changing to would be an eyefinity setup but I can't see myself doing that anytime soon. I felt I needed to explain the cons more thoroughly but really IMO the pros far outweigh them.