No - actually Matt knows more now than Matt did when he first posted the hyphen blog entry - I may be mistaken of course - do you have a more recent comment from him than his mid 2007 announcement?
Personally, I would go with the official word on the Google web site:
from URL structure - Webmasters/Site owners Help
I have seen Matt Cutts point out on several occassions that underscores have a different meaning, and that they were indexed as normal characters at one point, and even if that does change in Google, there is no guarantee that the change will carry over to other search engines.
I have seen a lot of sources conduct basic tests to try to determine which method is better (such as the test at URLs (Update)) but most of these tests are from 2007 or before. Personally, though, I tend to be conservative and if a particular method has a historical track record of being well supported, I tend to stay with it until something comes along which is demonstatable as being an improvement.
The best way to learn anything, is to question everything.
Just to add a vote for Hyphens, I would also like to share an excerpt from Google webmasters Help which states that:
Consider using punctuation in your URLs. The URL http://www.example.com/green-dress.html is much more useful to us than http://www.example.com/greendress.html. We recommend that you use hyphens (-) instead of underscores (_) in your URLs.
For further reading, you can visit G webmaster help HERE
I use hyphens in my website. When I did my web construstion, I found most of people to use hyphens. I don't know the theory behind, but google tell me the truth.