The G series AF nikkors are made to cut the cost of manufacture since they don't have an adjustable aperture. Nikon apparently thought it would be more consumer friendly with it's lower price. I have a 24mm f2 AI that's a great lens for photojournalism, among other things. I use it constantly on my Nikon F2s and F4s. Sharp as a tack and I really don't have a need for that extra stop. I just may push the film a bit when I really need it. And when I'm working with a lens that has that wide an angle of view, just a quick manual focus works just fine for me.
Here's Ken Rockwell's review http://www.kenrockwell.com/nikon/2420.htm
At the current price range, in my view, it's an alternative worth considering.