Subscribe to Comments compatibility WP 2.5

I’ve just installed the “subscribe to comments” plugin, but it doesn’t seem to be working.

Two tests were made to see if the commenter would receive an e-mail once a follow-up comment was posted, but that didn’t happen.

According to the “subscribe to comments” site, the plugin works up to WP 2.3.1 (I believe).

My question: Is there a 2.5.-compatible version available anywhere? Or is there another “subscribe to comments” plugin I could use?

In particular, I’d like to find one that allows you to subscribe to comments without having to actually submit a comment.

Any assistance would be much appreciated.