I second that as I just switched to Thunderbird (TB) from WLM 2011. The
one thing I like in MS Mail/ News reader clients that TB doesn't offer
is the automatic marking of all news messages read when you switch from
one news group to another. I wish TB added that capability in some
future update.
When you've done reading in one NG in TB, just press Shift-C to mark the
whole group as read. Takes half a second... Then I click the Next button
to go to the next unread post in the next news group. (Added the next
button by customising the button bar - easily done, just drag & drop).
HTH