Google, Yahoo and MSN Search
My primary search engine is Google. My Firefox defaults on Google home page. I use it every day. However, I must say that it has a very strong bias to older websites. Newer websites will rank much better in Yahoo! and MSN. I have a relatively new website (9 months) that does not make to the top10 SERP if Google but makes on both Yahoo! and MSN top10. So, if I want to search for some new websites, I would rather go to Yahoo! or MSN.