My customers and myself definitely get better rankings in Yahoo and I am convinced our sales result from that as well - I tracked it.
Earlier this year during the
SEO congress there was an interview held with one of the Search managers at Yahoo (Jon Glick) about the new search engine etc.
I quote one question and answer (which in my opinion might have a lot to do with what your are seeing) from this article:
"o Mike:
On the subject of meta data, let me just go off at a little tangent here. Tim [Mayer] mentioned to me yesterday that meta keywords are back again! After all that time away, now they're alive and well at Yahoo! search...
o Jon:
Yes we do use meta keywords. So let me touch on meta tags real fast. We index the meta description tag. It counts similar to body text. It's also a good fallback for us if there's no text on the page for us to lift an abstract to show to users. It won't always be used because we prefer to have the users search terms in what we show. So if we find those in the body text we're going to show that so that people can see a little snippet of what they're going to see when they land on that page. Other meta tags we deal with are things like the noindex, nofollow, nocache we respect those. For the meta keywords tag... well, originally it was a good idea. To me it's a great idea which unfortunately went wrong because its so heavily spammed. It's like, the people who knew how to use it, also knew how to abuse it! What we use it for right now is... I'd explain it as match and not rank. Let me give a better description of what that really means. Obviously, for a page to show up for a users query, it has to contain all the terms that the user types, either on the page, through the meta data, or anchor text in a link. So, if you have a product which is frequently misspelled. If you're located in one community, but do business in several surrounding communities, having the names for those communities or those alternate spellings in your meta keywords tag means that your page is now a candidate to show up in that search. That doesn't say that it'll rank, but at least it's considered. Whereas, if those words never appear then it can't be considered. "
Very long article but well worth the read....
http://www.e-marketing-news.co.uk/april_2004.html