I originally posted a question on Geospatial indexes here http://www.sqlservercentral.com/Forums/Topic651318-391-1.aspx.
I'm still not clear on the subject so should like to request an article on the subject. I've not been successful Googling or Binging the subject so I am guessing that it is a little understood subject.
One of the things I'd like covered is the effect of teh different index densities at different levels.