I just drifted to gmail. Not sure why, other than I use lots of other google freebies and Yahoo is generally in decline. Gmail threads can still be confusing but I think that I have even become comfortable with that. Once syncing between my trusty old Palm Treo and Yahoo finally ceased, Yahoo lost its one big advantage.
My main use of Yahoo now is its groups. I "own" multiple Yahoo groups. I still do not understand the advantages, if any, of newer flashier group functions such as facebook. I have an ... account, membership, whatever ... in facebook but do not use it other than to respond to an occasional message from someone who found me.