As soon as we let people lose on the final test server with live data, people started finding lots more bugs. Which means that the final switchover will be delayed for a while longer.
But, the NGS data is live and replication packets for the NGS data are flowing. I’ll post instructions on how to tap into this feed later today.
UPDATE: Please be careful with your edits — we plan to keep this data!. Unless some data corruption bug is discovered, we’re going to do our best to keep this data. Please keep this in mind as you edit on this server.
MetaBrainz Blog 
Will all the edit changes on ngs.musicbrainz.org be kept after NGS goes live on musicbrainz.org?
The blog post has been updated since Atedos’ question, but to re-confirm – YES – hence the big warning on ngs.musicbrainz.org :]
Looks nice. The new GUI seems easier to work with, but how do I switch artist/title for various artist releases?
Staffan V: Unfortunately you can’t at the moment. Quite frustrating! It’s logged here, so you can watch this issue if you want to know when it will be supported. http://tickets.musicbrainz.org/browse/MBS-1579