@smogsy cheers, got it sorted now.
Screen is stunning, I'm really pleased with it. I'm using it as a second screen for 3rd person games and also as a Netflix/Prime screen. I just think it's too large to use as a desktop screen, but already the colours etc. on my x34a are starting to look washed out compared to the OLED.
I'm trying not to jump around too many games as I get to grips with the best settings, so I'm playing Star Wars Fallen Jedi for the time being. 4k is a no go as my 1080ti can't push the pixels (is it pixels?) fast enough. However, I've dropped to 2560*1440 in the game settings and it's playing lovely with a solid 60fps. It doesn't feel like a compromise.
I'm now going to swap to my Vega 64 rig and see if Freesync is making a difference. I'll post thoughts later.