The 100mm E Series makes a cheap alternative to the highly regarded 105 2.5. Whilst the rings are plastic the barrel is metal and focusing is smooth and precise with the lovely viscosity of classic manual Nikkors - it's far better than the shorter E Series primes. Aperture stops are easily found, but the ring is a little sloppy in feel. Usual colour hyperfocal distance marks and IR mark are present.
If there is just measurable distortion I've been unable to detect it and I've not managed to produce chromatic abberation/fringing. On a 1.5 crop sensored body, I can detect no visible light fall off even wide open.
Sharpness wide open is very good, stopped down to f4 it's superb. Out of focus areas are rendered fairly smoothly at f4. Flare resistant isn't great - If the sun is near the subject the otherwise very good contrast drops. Colour saturation is good but not astounding.