Optimize for google is a good advice , my sites are on top three rankings for every keyword I optimize for and that brings not much traffic yet.
Msn says that they care that the site should not have html etc errors (w3c compliant) , most of my sites are not perfect.
They care about on site optimizations much , domain name like google and keyword rich urls are good.
But again nowadays it is not worth the effort unless you have a site for children or woman (when I told this before people found it offensive
, but what I try to say is children and woman are not too conservative about the search engines (at least a part of them) but especially tecnical man cares about them more and they hardly change them.
It took me one year to leave infoseek for google
All of my friends were saying hey this is a great search engine , it covers a lot more sites , you can find russian sites with it too , etc.And I did not cared.