Rated 5 out of 5 stars

Excellent, thanks. I've been following your work with GSOC and was looking forward to using it in real :)So far, so good!

Question: is there a criteria we can use to build our own Saved Search for mails still pending for reply?

This review is for a previous version of the add-on (0.1). 

I'm glad you like it. The messages are marked by adding a custom string attribute to the header. Looks like saved search can't find this attribute. I'll look into how they implement saved search and try to add it in. The workaround is to use the "List Messages Expecting Reply" button to show messages currently marked expect-reply.