Fons, I just picked up that 300 f2,8 two weeks ago, and am still trying to find out how to make the best use of the lens.
Yes, I certainly like it a lot. It's almost permanently attached to my camera. It has excellent sharpness and really seperates a subject from any background. There are a few drawbacks, but I think this will be a lens that I will happily use as much as my 55mm f1,2 or 105mm f2,5.
I must admit that, until recently, the lens was on my wish list, and ever has been since around 1996 (when they were still sold new), but I never imagined buying one. Just recently I had been stashing some money with the thought of buying a smaller and lighter camera to carry around. With that money on my bank account, I encountered a real good deal on a 300 f2,8 Ai-S which looked to be in good shape, so I realized that dream, and have not regretted it since.