SEOLinkVine is a blog network. If you need more clarification, you can read my earlier post on it here and watch the videos. Do not join with the "me too" attitude. Join if you intend to use the network and post articles to it. You will be wasting your money if you join to post 2 or 3 articles a month. If you understand the benefits of thoroughly spinning and quality of backlinks from other blogs and intend to post 12 or more articles a month, you will likely get your value of the service. Yes, I use it and it has delivered as promised.
If you are serious about your business, I suggest getting in now. If you are just a part timer or new to all of this, please do not join. There will be other blog networks from Callen I am sure. I just do not know when though. I will keep you posted as anything Callen puts out, I usually buy.