It doesn't just "track flight paths".
First, it has to get the data -- which covers everything from radar skin-paints if the aircraft transponder isn't operating, to unpacking the data that that transponder is sending (which could include anything from a simple 4-digit number to altitude, airspeed, heading, etc, etc.). Oh, and it has to raise appropriate alerts if that 4-digit number happens to be one of several special codes (indicating anything from voice-radio outage to a hijacking). There are plenty of other sources these days of location data too, (aircraft position/speed info relayed via satellite, for example) I don't know how many are integrated into this new system.
It has to present subsets of that data to particular controllers' displays, not every controller sees everything, even in a given range. That would be crazy-making. And controllers have to be able to hand off flights from one to another, so there's the whole UI, authentication, confirmation, etc, etc, there.
Naturally everything has to be recorded and logged, and queryable.
It has to project flight paths, and then analyze all that for possible intersections and raise appropriate warnings.
It also needs to be aware of airspace limitations -- which are frequently updated -- so that information can be displayed to controllers too. So there's another UI, to input those changes, along with the authorization, authentication, etc for that. Ditto with severe weather -- so it needs input from weather radars, etc.
It has to be able to cope with sudden changes to the system, like if an airport or ATC center suddenly drops out for some reason. (Weather, power failure, earthquake, terrorist, whatever.)
The distributed nodes in the system (airports and flight control centers) have to be able to communicate with each other with minimal latency and despite node failures, cable cuts, microwave tower outages, etc, etc.
The finished system has to be deployed across hundreds (thousands?) of flight centers and airports big and small (basically, almost anyplace with a tower) across the country in a way that it all works with the in-place systems everywhere else. There has to be room in those airports and flight control centers (most flight control centers are not in airports, BTW, there's no need for them to be. The controllers aren't looking out the windows. Airport ground control (the guys controlling aircraft taxiing) and approach/departure control is.)
No, this is not just a souped-up iPhone track-your-flight app. It's something responsible for the lives of millions of air travellers (not to mention air cargo flights) a year.