This question has come up before in other forums. I have two 28/3.5 AIs, a 28/3.5 'K', an H and a cm. They are all good. The 'K' kas better coating that the two older lenses. The AI lenses are very good. It doesn't matter to me that the 28/2.8 AIS has CRC and is sharper in the close range. I always carry a macro lens anyway. All ofthe 55/3.5 Micro Nikkors from the Micro Nikkor Auto compensating lens to the 55/2.8 AIS are much sharper than the 28/2.8 AIS in the close range and have much less distortion. If I need the effect of closer focusing with a 28 I can use a 28/1.8 Konica UC Hexanon. It also has a floating element design and is faster. The old 5mm Canon manual extension tube can be used with a number of Canon 28mm lenses. At the right price I wouldn't mind adding a 28/2.8 AIS to my Nikon collection but I wouldn't expect any improvement over the 28/2.8 AIS in regular shooting and I also wouldn't expect it to be nearly as good as a Micro Nikkor in the close-up range.