I use this plugin with WPMU where I have installed domain mapping. I have problem to catch to which site relate the error logs 404.
In columns URI I see part of URL (/sitemap.xml.gz) without knowing to which site this 404 error belong. Often there is no reffer URL.
If you ban some URL for 404 error, It could be nice to know which site there tried to reach, for me this mean to know where i could have some problem because of wrong URL or name etc.