Which states they won't tell you the details. But they will tell you the limitations.
Q. What are the limitations of Media Composer | First compared to full Media Composer?
A. At this time we aren’t releasing detailed information on the feature set, as Media Composer | First is still in development, and won’t be available until later in 2015. However you can expect a limited feature set that makes Media Composer | First less intimidating to new users, but also less appealing to power users. You can expect fewer settings, menus, timeline tracks, monitor features, bin features, titling features, effects and other features than the full Media Composer. You can also expect that Media Composer | First won’t work with Avid Interplay Production, Interplay MAM, or MediaCentral UX, and that shared projects won’t be supported on ISIS storage systems. In addition, all projects will be stored in the cloud, and you’ll get a limited number of projects and a limited amount of cloud storage space. There will be options to expand Media Composer | First, from additional project and storage capacity to plug-ins, options, and additional applications to stock footage and music to upgrades to the full Media Composer.
Walter's link (above) about the Blackmagic IO card specifically talks about four video tracks and eight audio tracks as limitations. It is always a problem to decide on how to cripple a free version. Eight audio tracks! Sound familiar.