I use an AIS-S 28mm 2.8 on my full frame Nikon, and love it.
I also have the 28mm 2.8 af-d and use it on a D300. I know that it does get a lot of flack as a lens but I took it on holiday recently as my only lens and found it a very useful focal length on DX. I genuinely dont think that the image quality is as bad as a lot make out, unless pixel peeping at 100%. The centre is very sharp on DX and so presumably FX, although I havent really used it on full frame so dont know what the corners will be like.