A question that I am left with after reading this excellent book is if the factors that Diamond claimed resulted in certain nations starting the "race" on the starting line ahead of others have been erased thanks to globalisation and the ease of transport, what factors now can be used to determine which nations will get ahead of others? Firstly, I am not too sure that globalisation has erased all these factors, and secondly, I think this points towards the need for another book discussing the issue of dominance in our contemporary world.
The one thing that I really wonder about is how Diamond could account for the success of the Mongols. Diamond's overall arguments seem to imply that the Mongols (as a non-agricultural society) should have had a hard time building a state and should not have had any real chance of defeating the Chinese and subjugating them for a long period of time. Diamond tries to tie this to geography (the open plains where the Mongols did well) but he does not really get into this in any systematic way.
This makes me wonder if there might be other cases that would tend to disprove his theories but which I do not know about.