Matt Cutts finally chimed in on the big buzz about Hyphens & Underscores Are Now Treated Equally in Google.com, which was broken by Stephan Spencer at News.com.
Matt said, he "didn’t quite say that in the talk." What he did say was that Google was "looking at that now" and it is NOT a "done deal at this point."
Matt does say that if you do have a site with underscores, that at this point, it is not worth revamping all your URLs to use dashes instead.
But he does and a very important note:
If you’re starting fresh, I’d still pick dashes.
So Matt is still recommending that you go with dashes, if it is easy to start off with.
So there you go. Currently, dashes and underscores are not treated equally in Google.
Forum discussion at WebmasterWorld.