Segmentation options are rather limited right now. Even a simple set of "I'm interested in" options for subscribers isn't possible. This could be significantly improved in two ways:
  1. add the option to segment based on wp_usermeta fields. This would allow me to gather subscriber information by many other methods (Gravity Forms, Buddy Press, etc), and then create email segments based on that.
  2. add a PHP API which would allow me to define my own segments by any criteria I want. While this would require a developer to take advantage of, it might make it easier for creating new segmentation options in MailPoet itself, so possibly worthwhile for both third party and your own developers :-)