I bought a 180/2.8 ED~AI-s in the spring of 1986. I still have it. I used it along with several more modern lenses during model shoots, in 2014. The results were indistinguishable between the several lenses. I was surprised. It is a good focal length of lens to have, especially outdoors. Indoors,especially when using flash, it might be less-useful than a modern 70-200/2.8. There is also very little discernible difference in performance between it and the more modern AF or AF-D 180mm lens models, both of which I have also owned. Thirty years ago, zoom lenses were nowhere near as good as modern zoom lenses, and my feeling is that a modern AF zoom lens offers a lot of local length flexibility,and thus a lot of options, which makes it a better studio and outdoor portraiture decision rather than a trio of three, or even a set of four,prime lenses
I don't consider the 180mm as a good portrait lens. For one thing, it's a roughly 4x lens (43mm diagonal), and compresses the subject a bit too much. For portraits, the 135mm is the maximum (head, and head and shoulders), and a 105mm for waist length (Some folks like the 85mm class, since it's 2x).
The 180mm makes a fine lens for journalists, along with the 105mm f/2.5, and a 50mm f/1.4. I use mine a lot for landscape when I can't get really close. It's most often paired with my F3 and FM2n.
It's value is that it's a prime lens. I do have an 80-200 f/4, but I'm still of the opinion that the best lenses, especially from the AI and AI-s era, are the primes.
I found mine in pristine condition. This lens is not well known by many but according to the folks who really know lenses, it is one of the best at color transmission, contrast, and sharpness.
I've never owned the 180. I've owned several Nikkor 135s which I liked and I didn't think the difference between 135 and 180 would warrant buying one. I could just take one step closer and save $$$.
They are reasonably priced on the auction site as well as used gear sellers. A very nice one can be had for $300 or so. There's one on there right now for $199 that is used looking outside with very clean glass.
Still waiting on the right price for the Ai-s but got a good deal on the Nikon 180mm f/2.8AF like new for under $300. Still want the Ai-s, love these old manual lens.
There is very little to separate the AI-s from the AF incarnations...there are advantages to the AF-D iteration...I expect you will be happy with the AF version you bought...