There is some early discussion over at WebmasterWorld that Microsoft Bing has updated their search index. Many webmasters are discussing changes in rankings in this and other forums (which are hard to link to).
Here is what WebmasterWorld moderator, martinibuster wrote:
Bing engineers may need to refine their trust algos. I'm seeing a SERP where Bing is giving a poor quality subdomain a pass because the main domain has a high amount of inbound links (nearly a million). I think Bings method for determining sites likely to be authoritative needs tweaking.
Interestingly, Bing produces another result not seen in the other search engines that is actually pretty good.
For this site, I can tell you Bing sends up more traffic than Yahoo.
The last Bing update we reported was in late October.
Forum discussion at WebmasterWorld.