Highlights include Sliding Sync (instant login/launch/sync), Native OIDC (industry-standard authentication), Native Group VoIP (end-to-end encrypted large-scale voice & video conferencing) and Faster Joins (lazy-loading room state when your server joins a room).
There do tend to be in logical groups, e.g. you’ll see all of Mozilla’s stuff in their server - but there are quite a few general purpose servers.