taps - 9:30 am on Aug 17, 2005 (gmt 0)

We've lost 80% of traffic by simply changing filenames from mixed uppercase/lowercase to lowercase only. It took us three months to come back.

If your traffic is already at the bottom it might be a good time to change filenames. However: Google might have crawled you again and maybe you are ready to bounce back on top with the next major update. If you change filenames now, maybe you'll loose the chance to bounce back.

If you're going to change filenames, use 301 redirects from old to new filenames.

IMHO it is much more important to solve all problems related to duplicate content. If you already did that and if you like to take the risk, go ahead.

Maybe a cleaned up site with new filenames will come back better than ever.