I had a Series E and later replaced it with the 28mm f2.8D AF. There are three different 28/2.8 lenses. The Series E is a 5 element design, while the AiS is a more complex optical formula. The Series E optics were also used in the original version of the AF 28/2.8 lens. It had a poor reputation compared to the AiS, so when Nikon came out with the D-version of the 28/2.8 they redesigned the optics. I have not shot the AiS, but the AF-D version is sharper than the Series E and original AF. Main difference is wide open. Stopped down, the Series E is actually really good. The AF-D is fairly cheap used, so I'd probably go for that over the Series E if you cannot afford an AiS, which costs more used.