Rated 4 out of 5 stars
I would have expected the add-on to behave like the gmail conversations in the way it physically groups them together, but it doesn't. This is what I like most about the conversations feature of gmail because it keeps the inbox nice and tidy. Future versions of this add-on should work on including this part as it's really the most valuable feature of conversations. Unfortunately without this feature this add-on is not useful for me.
EDIT: View > Sort By > Threaded works perfectly! Rating upgraded :)
Have you given, in the menus, View > Sort By > Threaded a try?