I feel I've posted a bit too much to this thread lately and people will be getting sick of hearing from me, so I'll keep this brief!
I promised to report back on my first few days with the LG monitor.
I unboxed it last Friday evening and although I used it a little over the weekend, it wasn't until Monday that I started using it for long periods. I've now completed 3 solid days of use and am into my fourth.
I'm pleased to report that the display is working fine at 60Hz on my nMP. OS X Yosemite 10.10.3 certainly seems to provide stable drivers and the problems that others have experienced have, thankfully, not happened to me. (I await darkenergymedia's return with interest to see how he's doing!)
I was previously using a 30 inch Apple Cinema Display and while that screen was great, it's not until you start using a HiDPI screen like the LG in a scaled resolution that you start to appreciate the clarity. I do lots of design and coding and this is much better for my eyes, no doubt. I'm running in 2560 x 1350 scaled, but if your eyes are a little better than mine then probably 3008 x 1586 would be better and closer in relative size to old 100ppi 30" screens.
The other important factor for many of us is colour reproduction and the LG doesn't disappoint. I'm running in sRGB but will also use Adobe RGB when I'm doing print work. The depth of colour is really noticeable when compared to my old ACD.
Only problem I've noticed (and it's a tiny one) is that if I turn the monitor off (e.g. when I go off for lunch) then when I come back and turn it on, although OS X is in the correct scaled mode, application windows have either moved or resized slightly as if the display is momentarily in a different resolution before it switches to the right scaled one. That'll be down to OS X, of course, nothing to do with the LG and it's not a big problem.
I said I'd keep this brief, so I'll stop there. No complaints. It's all good.