With the release of new lenses, a lot of good older glass gets tossed by the wayside. A lot of people forget that good glass was around long before great digital bodies. A lot of old glass is still great and still useable as was presented in the opportunity to shoot a good 300mm f/4.5 AI-S lens by lens owner and my friend Paolo Capili at Broadway Camera. A manual focus lens, it still is a super lens. Back when the 300 f/4.5 AI-S was still king, the manual focusing system was a lot tighter and easier to focus in manually than the AF-S of today. Today's AF-S systems are kept loose so as the autofocus motors aren't fighting lens tightness in order to focus in on a subject. But the manual focus systems back then were keyed tight so that you wouldn't lose focus easily once you got it.
This lens is sharp. If I wasn't into nature/wildlife photography, and having to pre-focus a pain in the tail-end, I'd be considering this lens. It's a large lens, about 3/4s the size of my 70-200mm VRII and very solid in construction. I could have upped the shutterspeed a bit more on these two test shots since they were a little hot (bright). But you get the picture as is and very sharp.
In conclusion, don't count old glass out. Especially ones of the calibre of this. Try them out, shoot them, test your manual focussing skills and above all, they're like shelter pets. They deserve a home. Why not give them a home in your camera bag?