What difference is there between the paid and free versions? Just no ads?

I've just put my 8 flights into it for the next couple of weeks and the free version so far seems ok (except for the ads).

As for the actual departure and arrival times (and thus, the actual in-flight tracking), at least for the airlines I fly, Flight Tracker Pro were not that accurate, so if I had the need to track in real time, I used the Flightradar 24 app (although that was reliant on the aircraft having a compatible transponder, in my region, some of the older Embraer 190s don't have them).