Is it perfect? Not at all. The AI is a bit dumb (still dangerous, though), the map levels are often linear (though not always), and you'll feel like you're throwing spit wads at the Terminator units for half the campaign (though really, I would argue that this helps to preserve the 'unstoppable killing machines' trope of the first film).
But now, we're on to the good aspects of the game:
The devs absolutely 'nailed' the 80's VHS post-apocalypse atmosphere depicted briefly at the beginning of Terminator 1. The bleak, grayish lighting, the well-implemented film grain effect, and the absolutely 'perfect' soundtrack make for what is, unqeustionably, the most faithful depiction of the dark world of Terminator to date.
The difficulty is highly customizable, even in-game. Anything from HUD disabling/limiting to enemy and character health display disabling and navigation marker removal is free for the player to tweak at their whim. This is a welcome change from the AAA insistence on wresting any and all control from the player's hands, and I hope to see it more often from middle-market and indie developers.
The storyline completely ignores everything that happens after T2, and as one of the remaining Terminator fans, I couldn't be happier. This alone was reason enough for me to have bought this game on Steam (wish I had known about GOG sooner, but I digress), but the fan-service (which is actually good and fitting here, and not lame) made the experience even better. If you're a fan of the series, the plot twists probably won't come as much of a surprise to you, but are still a nice wink and nod to classic Terminator.
All in all, I would rate this game as a solid 8.5.10
After enduring an onslaught of increasingly bad works of fan-fiction that dared to call themselves 'Terminator films', I can finally say that 'Jugdement Day' has the sequel it deseerves.
Buy it or face termination!