Support for Team blogs : This is just a grouping of existing blogs, not actually something new we parse. The idea is to give some exposure to a team someone works for - for example, a specific PostgreSQL support company.
Top posters list : The list of all subscriptions has been replaced with a list of top posters. The list was becoming a bit too large to manage, and didn't really fill a purpose. And it was hard to integrate nicely with the Team blogs feature.
There has also been a bunch of internal changes : Details available in the git repo on http://git.postgresql.org.
If you want to make use of the Team blogs feature, this has unfortunately not been implemented in the admin interface. We (well, me, really) were just a bit too lazy for that. So if you want to make use of it, please just send an email to firstname.lastname@example.org letting us know what name you want for the team, and which blogs to add to it (these blogs should already be subscribed to planet).