The game's rendering engine and simulation components are actually pretty impressive all in all. Graphically the game does look a little bit dated; even the initial releases of Freepace 2 or Independence War 2 from several years ago provide a more convincing (or at least snazzy) rendition of space combat in a lot of respects. But Tomorrow War still isn't all that bad in this department; the ship models are quite detailed, with visible weapon hardpoints, animated maneuvering thrusters, and a variety of high-powered thruster effects. There even seems to be some form of damage modeling that actively applies scarred texturing to fighters and capital ships as they take abuse.
I should also give special mention of the game engine's much-hyped ability to take you from an orbital plane down to a planet's surface in real-time. The last game I saw try this was Breed, and I have to say that Tomorrow War provides a much more convincing rendition. There's no sensation of suddenly being 'teleported' to a separate environment - you always get the sensation of smoothly descending through the atmospheric layers until you finally start seeing land details from close-up. This is a pretty cool feat (especially with the sheer amount of terrain provided), and is only diminished by the fact that there really isn't all that much to do or explore outside of the scripted mission protocols.
The gameplay itself is pretty solid too. You can pick between either an "arcade" or "simulation"-based flight model (or a hybrid of the two), which basically affects if you need to fight inertia when swinging your fighter around and how much you'll need to work the lateral thrust controls. Embarrassingly I actually had a lot of trouble getting my fighter going where I wanted it to during combat on the full-blown simulation mode (proving how long it's been since I last broke out a session with Independence War), but found the hybrid mode worked best for a balance between realism and fun.
For the actual missions, the developers did their best to keep the emptiness of space interesting with a variety of objectives and environments; one mission may have you going up and down between space and the atmosphere a number of times in pursuit of objectives, while another may have you trying to navigate a dense asteroid belt at high speeds. The game also sets up some pretty cool large-scale battles between armadas of fighters and capital ships, although it's so easy to die in these fights with no clear idea on what happened (generally a ship collision) that they can rapidly become frustrating.
But the campaign is nearly ruined by the fact that the in-flight dialogue is broken. Apparently throughout the missions, there is supposed to be all sorts of radio chatter flying around to actually advise you on why you're there, what's going on, and what you're supposed to be doing. The problem is that you never see or hear any of this radio chatter from the cockpit, and only until you figure out that the dialogue that is supposed to be there is actually being transcribed in your character's Journal (a separate interface that's very clumsy to bring up in the middle of a pitched battle) will you actually have any clue about what's going on.
Digging into this, I found comments on the game's official forums that much the voice dialogue on the English version of the game is actually broken, with no word on a fix. Given how a problem like this all-but destroys any remaining sense of plot and immersion the game may have offered, I'm actually surprised a critical problem like this isn't being addressed more directly by the development team. This just makes the campaign's other faults more painful; the AI's quirkiness for example, and the random chance this has of causing a given mission's scripting to break due to a single fighter not joining up in formation properly in order to trigger the next event.