Is it Worthwile to Change Underscores to Dashes?

[zampik]

I have a niche website with about 15 pages, all indexed on google etc and got listed on ODP.

I wasn't really aware of this using dash in folder names and url tip until now.

My site is pretty new (has about 60-70 hits per day)

My current site structure is like this;

../widget_categories/brown_widgets.html
../widget_categories/red_widgets.html
../widget_categories/white_widgets.html

Do you think it might be worthwile for the future and worth losing some visitors for about a week (i figured that was about the time it takes google to index my site completely) to switch to the site structure below?
(about 80% of my visitors are from google by the way)

Structure that I am thinking about switching to:

../brown_widgets/brown_widgets.html
../red_widgets/red_widgets.html
../white_widgets/white_widgets.html

I would appreciate your advice...