mod_rewrite: *.html to */

Hi,

I just switched from MT 3.2 to WP 1.5.

My MT url looked like this: https://www.chapatimystery.com/archives/homistan/softer_side_of_freedom.html

My WP url looks like this: https://www.chapatimystery.com/archives/homistan/softer_side_of_freedom/

I am using the dash-to-underscore plugin shipped w/WP.

To keep my old permalinks active, I added .html to my permalinks structure. But, I would rather redirect people than keep .html at the end of the url string.

My question is that my mod_rewrite just doesn’t seem to work. I have this
RewriteRule ^archives/(.*)/(.*).html$ /index.php?category_name=$1&name=$2 [QSA,L]

subsequently, is there an harm in keeping html around?
please help.