If I want relevant results I use google. The only time I use yahoo/msn is just to see where I am ranking.
Almost the same here
I do however also use the Norwegian search engine Kvasir.no a few times, it's powered by Google though, but filtered differently with norwegian results.
I use Google more often for my SEO analysis. But if I really want to search for something on the net and expect good results from my search - I use Yahoo