While I (curiously) haven't seen anything surface yet in the blogosphere, there's every indication that Windows Live Search (MSN) has rolled out an algorithm update in the past few days. I've seen radical ranking changes for the keywords and sites I track, and confirmed with at least one other senior SEO that this has been observed elsewhere.
I'm certainly not one (especially keeping in the spirit of SEO Skeptic) to make sweeping claims about what any alogrithm update has accomplished (it's been kind to the sites I work on, but it doesn't mean it's a "good" update). At first blush it appears as though Live is giving a bit less credit to keyword use in domain names and URLs – which traditionally has always been problematically over-emphasized in Live's ranking criteria (how 1995, how Microsoft).
And there's some indication – still, based on a superficial look – that Live is now better job of stemming. I'm not sure if others out there have noticed this behaviour, but Live seems to always had problems in particular understanding that the singular and plural form of words have something to do with each other. Combined with Live's over-emphasis on keywords in domains, this means you could be hooped for "cars" even if you ranked well for "car" with your domain of car-mart.com.