The minor-leaguers aren't going to be great, simply because Detroit doesn't have any great minor leaguers to trade, and Rabelo's not especially interesting. But Maybin and Miller are both potential superstars. I imagine Miller would join the Marlins right away. Maybin probably needs a little more time in the minors, but he's close to being ready to contribute too.
UPDATE 6:47: The Detroit Free Press and other sources confirm this one. The other players heading to Florida include pitchers Burke Badenhop and Eulogio de la Cruz, and another as-yet-unnamed pitcher. Badenhop is a groundball-throwing starter who's going to have to strike out more batters or move to the 'pen to have much success in the majors. De la Cruz is a hard-throwing righty who'll probably be used as a reliever.
With this trade and the Edgar Renteria deal, the Tigers' farm system is officially kaput. Other than their 2007 draftees, there is nothing left in it. They need to hope Cabrera can get them back to the World Series, because if he doesn't do it, it's not going to happen again for a while.