Wordtracker.com shows MSN as having 21% of the search traffic. I don't think it's that high, but i get good traffic from MSN for some of my sites. Sometimes there is only a fraction of the competition for a keyword on MSN as there is on Google too. steve http://www.themoneymakersite.com
I have one particular site that's in top 10 for quite a few key words. Unbelievably, Yahoo is giving 4x as much traffic whilst ranking in the 30s-40s. However, keep in mind that MSN may gradually become some sort of juggernaut in the Search Engine world, so it's always good to optimize and try to keep rankings up in MSN. Plus, #1 anywhere is a good motivator Don't be fazed if MSN doesn't initially give good traffic, if Microsoft wins out, then you get to reap the rewards, if not - well, you've got some sort of investment there anyways Good luck!
I have quite a few words in the top 5 in MSN and yes I get very little traffic from them still. About 10% of my SE traffic is from MSN. Yahoo about 15% the rest is all Google. I guess we all have been brainwashed to use Google. MSN better start marketing hard.