If your site has been crawled for free it will be in the Yahoo index after the 15th when they drop Ink. It just won’t be refreshed every 48 hours.
Unless you have an auction site, or some other page that changes content daily, there is no reason to join Site Match, and plenty of reasons not to… that is if Yahoo delivers on its promise to fully crawl the web, which to say the least it has not yet, but in any case people should wait and see how fully your sites are included come the 16th.