On Wednesday, nine major publishers began publishing articles straight to Facebook under the social network’s long-anticipated product, called Instant Articles. Facebook sweetened the deal by letting publishers control the ad sales, branding and content; sell ads on the articles and keep all the revenue; and get data on their readers.

Still, publishers were mixed in their embrace: BuzzFeed and NBC News were the only ones to go all in committing to using the product. Others, like The New York Times and the Atlantic, are taking a more cautious approach. There are still plenty of unknowns, chiefly whether Facebook’s terms will remain as generous to publishers as they seem to be now.