A combined 2160×1200 pixel format, means 1080×1200 each. According to iFixit each OLED display is 90mm for a resolution of about 456ppi, which means you’ll need to be 8 inches from the display to have a ‘retina’ experience — an experience where you can’t see individual pixels. (Your eyes are not far enough using the Oculus Rift and so you’ll see pixels.)
OLEDs have fast response times and are the only feasible display technology — manufacturing infrastructure, tech maturity, price, etc. — today that won’t make you sick due to pixel lag.