FSS is the scouting system that WIS instituted as the 'New' Potential. There are many opinions on it and the biggest drawback being that it really has taken a lot away from being able to develop your players as you feel fit via your practice plan and has shifted that into recruiting (ie if you want to develop a high PER sf you need to recruit one with either an already high per rating or one that has good potential as opposed from just giving him 20 minutes in PER and seeing it improve around 8-10 points in a season (which was how it worked in the old system))
You have to purchase states via the FSS system to get the info on each player's potential and states vary in price based on the number of recruits the said state.
The biggest benefit of FSS, imo, is the 'Word on the Street' Info that you get twice daily (approx 2 am/pm est). This tells you where said recruit is leaning and/or how big of a target said player is for said team