1. I notice I have all the features of my POTS line; same voice mail, same address book, etc.
2. Will this go away, once I port my old phone number and cancel my landline?
3. I am assuming yes, if not, why would I need the Premium service?
When you start new service you get two months of Premier Service for free. A trial period to see if you like the additional services/features. If you opt-out of the premier, then you fall back to Basic service which only includes VoiceMail, Call Waiting, and CallerID number (note, no callerID name). The Contact List (address book) in My Ooma is still available.
here is the link for the comparison between the two: http://ooma.custhelp.com/app/answers/detail/a_id/90/