Much has already been written on coComment — clearly there is a great pent-up demand for this kind of service.
I decided to try it out. My past approach has been to rely on TalkDigger to go back and look for comments I have posted, though URL search is not as good as an exact list of my conversations.

The way you track your comments with coComment is through a bookmarklet. They have specific ones for the four main browsers. The bookmarklet is supposed to allow you to both track your newly added comments and also add your old comments.
I tried it out in both Firefox and IE7 (and Maxthon, too, which runs on whatever version of IE is installed).

A couple things I noticed so far:

• The bookmarklet doesn’t appear to work properly in IE7 due to a script error. The same may be true of IE6, but I will have to restore my VMs before I can try that out.
• It works fine in Firefox when adding new comments (in both blogger and WordPress); however, I am unable to add my old comments. The FAQ suggests that a dialog box will appear, but it does not. Nothing happens.

It is a cool idea and I will keep evaluating it. I agree with Mike Arrington that including trackbacks would pretty much solve the entire problem of tracking one’s comments (and the responses to those comments); however, this is a great start.