It all depents on your situation. It's not completely clear, but I read through the lines that you currently use NS7rc1. In that case I would just do the updates through software center and you end up with a fully functional NS7 server as soon the final is released. (they will have the same repositories)
If you have NS6.8, it might be good to do a fresh install. However, 'our' devs will do their best to create a rock solid upgrade path.