MSN sends negligible traffic to my site. If they're the up and coming search engine, they are hiding that fact from webmasters.
Google gets my thumbs up not only because they send quality traffic, but they make the webmaster's job easier. Google's webmaster tools and Analytics work well, and their bot gets the job done in a hurry.
I'm not a conspiracy nut, but I wonder if Yahoo's mediocre traffic is punishment for refusing to choke up a yearly fee ($300!) for inclusion in their directory and ongoing fees for their "sponsored search" entries. They have a free submission process; I dutifully played that game for a year and always came up snake eyes. Each time I was reminded that they'd be happy to process my entry in less than 7 days IF I paid their yearly fee.
Yahoo is evil. I may ban their bandwidth-hungry bot on principle alone.