People have inquired about losing track of comments from older posts on Angry Bear, or lose track of the occasional comment but want to keep track of responses.
Cocomments service allows you to track comments from old posts and tell you about new responses. For some who visit multiple blogs and leave comments, you might find this easier than bookmarks and such. It can be difficult to remember a few days after a comment was left.
Blogger has a notification system, but requires a comment be left to activate it. And it will send you notification of your own comments. Let me know if the co-comments are useful…it is evolving quickly.