I just tried the game, and if this had been finished and released in 1985, it would have competed well with Elite on the C64.
It plays very much like the first Star Raiders game, but the joystick moves the crosshairs as well as the ship. Objects in space are rendered in what looks like full 3D line art, rather than simple sprites. And you can fly into planets' atmospheres to do strafing runs of enemy bases. I was awestruck when I saw the spherical planet come into view; it looked like something just a little beyond what I expected an Atari game to do in the 1980s. You're not used to seeing big ol' globes on an Atari 8-bit. You're used to seeing big flat raster sunsets, or if you're lucky, some clever animation like Rescue on Fractalus used. The plantery terrain wasn't quite as realistic as Fractalus, but was still very good, and very arcade-like.
The part that really shows the game's ambition is the galactic map. The game starts with "galactic history", a cutscene for lack of a better word, which simulates the progress of the Zylon fleet up to the point of the player joining the fight. The map is no longer arranged in a simple grid like the original cartridge. It contains not only enemy squadrons and starbases, but star systems with orbiting planets. It is an extension of the thing that Star Raiders always had that Elite didn't: while you were in your sector, time was still passing in other sectors. Even in the original Star Raiders, enemy squadrons would move to different sectors, surrounding starbases, and eventually destroying them if the player didn't intervene. In this sequel, new squadrons could also be launched from occupied planets. I haven't played the advanced levels yet, but I imagine the player has to choose carefully between defending starbases and raiding shipyards.
I've found no game-ruining bugs, but I am not sure whether the flight and combat system has been completely worked out, or whether I'm just not good at the game yet. If this had been leaked on a BBS, it would have been received so much better than the ones that were, well, actually leaked.