The "Auctiva store" is basically another tool to help you display and sell your items, not a means to replace an existing ebay store front.
Let me give an example, for those who use Auctiva but do not have an ebay store, it is a great way for buyers to see all your items at once in a store-like format. Buyers would just have to click on the link on the scrolling gallery and then they could view all of that persons items in a store setting without the person having an ebay store. Buyers would have to click on that link though to get to the Auctiva store...it just will not come up automatically or be offered like an Ebay store is offered on ebay.
For Ebay store owners, it is just another selling tool to use. I spend most of my time on my Ebay store front and have not spent as much on the Auctiva one. When I was only doing auctions and no store, I did push the link to my auctiva store a lot so people could see my items.
Hope that helps but if you need more info or help, just let us know.
Marcia