It’s everything ThirdWire ever made for SF2. Every game, every expansion pack, every DLC, the entire series in one install for $100. Given how much all of it costs separately, this is not a bad deal.
However, I doubt any bug fixing has taken place. Pretty sure most of the game still suffers from some game-breaking bugs that were never repaired. The stock enemy carrier groups don’t work, the AI don’t know how to use external countermeasure pods, you can’t fly campaign missions at night, enemy active radar homing missiles give no warning on the RWR, the list goes on.
However, if you want sim-lite and you’re willing to keep your scenario before about 1992, it isn’t terrible. It isn’t great, either.