We had this question come up on our OO forum....
If you research Stellar Cartography you can see the planets on the mini-map (otherwise you only see the stars). The question is, does having more planets in a system increase the chance of a habitable planet, or is the percentage the same no matter how many planets there are? In other words, is it worth heading to a system with more planets because the odds will be better for it having a habitable world?