Is it worth changing urls with underscores?

[Jingo01]

A few pages on one of my sites have underscores linking keywords rather than hyphens (keywords_and_keyword rather than keyword-and-keyword). Possibly from a time before I knew hyphens were preferred...

One of the pages ranks well, and drives a good amount of traffic. The others do not do so well, but are still within the top 10 landing pages for the site.

Is it worth me changing the underscores to hyphens (setting up 301 redirects first of course) or doesn't it make that much difference?

[EGOL]

Let's say that you gain a tiny advantage by changing... and.... Let's say you give up a tiny advantage by redirecting (lots of people believe that the links into a redirected page to not pass all of their ranking benefit to the new URL).

Based upon that you cancelled out some of the benefit - maybe the loss was greater than the gain?

So, if it was my site I would stick with what I have and use hyphens for all future pages.

[firstconversion]

Ive never seen any benefit proven and certainly wouldn't bother. Here's a short video from Matt Cutts answering just this question