I've managed to play a little on the monitor and I'm really impressed with it. The Witcher 3 was literally the best looking thing I've ever seen on a monitor and was just so smooth. Also played Fallout 4 - which really should be a pants experience on this set-up (apparently it doesn't support G-Sync, can't support SLI and not only has a framerate cap but also ties its physics to the framerate) and I have to say it was flawless. I set a 70fps cap in inspector and forced V-Sync off whilst leaving G-Sync on. No lag, no stutter, no tearing - perfect smooth gameplay.
Also did a few hours work on it and I love the additional space over 1080p. I've tweaked the colours to my liking and honestly love the picture. I'm sure it's still well below a good IPS but for me it's marvellous.
I'm in two minds whether to return it or not. On the one hand it bugs me that I've spent £500+ on something that isn't perfect. On the other, I'm not sure if I might end up with something worse and hate the hassle of going through returns processes!