I actually don't track what traffic comes from which search engine; I don't track my SERP ranking in search engines; I don't worry about pagerank.

99% of my traffic comes from word of mouth. It comes from my participation in Yahoo and MSN communities filled with people willing to purchase from me, from previous customers, or actual selling in the real world. In my retail business, I would rather have repeat customer than 1000 visitors a day who don't buy anything.

If I were to concentrate all my efforts on search engines, I would work with Yahoo and MSN because they have the repeat visitors who are more likely to do searches. I don't usually use Google myself, only as a last resort.