Since a few have posted their framerate/frametimes graphs, I'll post one of my own from a play session I just had.
First, my specs:
OS: Windows 10 64-bit
Nvidia Driver: 372.54
Display: Acer Predator XB271HU
Motherboard: ASRock Z87 Extreme4
Power Supply: EVGA SuperNOVA 750W G2
CPU: i7-4770k @4.2GHz
Heatsink: Hyper 212 Evo w/2x Noctua NF-F12 Fans
GPU: GIGABYTE GTX 980 Ti G1 Gaming 6GB
RAM: 16GB G.SKILL Sniper DDR3 @1866MHz
SSD (OS): 256GB Samsung 850 Pro
HDD (Games): 5TB Western Digital Black 7200 RPM/128MB Cache
I'm running it on my 5TB drive with Hyper-threading disabled on my CPU, 16x Quality AF forced through Nvidia Inspector, Maximum pre-rendered frames 1, Prefer maximum performance, Shader Cache off.
In-game settings are maxed, FXAA, Fullscreen, Mouse Smoothing 0, 2560x1440 on a G-Sync 1440p monitor.
But for that spike at the beginning (may have been the load screen at launch, or a jump from one galaxy to the next early in my play session), not too bad. It may be a little bumpier than average, thanks to the G-Sync's variable refresh, and is anything between 55-100+ during gameplay. I will say that perceived frametimes are at their worst when I first pull out my visor to scan while on foot, but otherwise, everything is pretty much stutter free. Who knows, might be the magic of G-Sync making me perceive it is smoother than it actually is.
I can only guess that the complaint of frequent stuttering/bad framepacing is down to double-buffer vsync, or weaker CPU's. As for higher end systems experiencing the problem, I'm at a loss.