Finally seeing the benefits of upgrading to 16gb a few months back. I knew it would come in use eventually!
I don't get any stutters at all on my 980ti @ 1440p, max settings, fxaa. It's just fps isn't as high as I'd like. Get around 50fps average (not that I've benchmarked it properly, just a overly cautious estimate). I think overall the engine is well optimised, it's simply very graphically intensive.
However there are places where the fps is lower than you'd expect and some places it is higher than you'd expect. For example, there is cave area where fps was taking quite a hit, yet it was a closed off area, with not much going on. Soon as I walked outside into an open jungle like area, the fps shot up. I'm not sure whats causing it but I did notice the fps dropping when the glow stick is being used.
One thing I'm happy about is that there is no mouse stutter. The 2013 had terrible mouse stutter.