[overcast]

Actually the Earth is nearly perfect, far more perfect than most any sphere with interact with in day to day life. The equatorial bulge is 20 miles or so, which is approximately .33% Technically an oblate spheroid, but barely.

[evanpw]

There's a great Isaac Asimov essay on this topic: http://chem.tufts.edu/answersinscience/relativityofwrong.htm

[overcast]

Great find, thanks!

[jameshart]

And for comparison, the variation in surface height relative to sealevel is over 10 miles (6 miles down to the bottom of deep ocean trenches; 5 miles up to the top of mountains)