I'm a little saddened to see that (as I write this) Metacritic still only has one review up for Tactical Assault, and it's a low rank by a magazine without an online version. The game itself is quite good, and frankly deserves better.
In terms of space travel and combat, Trek was realistic only in the very broadest sense. For example, the ships depicted in the series were always seen with the same orientation and in the same orbit. Granted, audiences might have been confused by vessels at all angles to each other, or by real inertial behavior. Also, for the most part, strategy was limited to capital ships pounding away at each other, almost like naval vessels. (See also: KHAAAAANN!)
So the decision to limit combat in Tactical Assault to unwieldy starships in a 2D plane may be unrealistic, but it's true to the source material. Set at around the same time frame as the original series movies, the campaign centers on conflict along the Neutral Zone between Klingon, Romulan, and Federation ships. Like the original series, it makes handwaves to diplomacy, but like Kirk it defaults to phaser blasts quickly.
The "tactical" part of the game is basically a tension between six-sided shields and slow-to-charge weapons. Keeping your strongest shields aimed at the enemy while concentrating fire on their weakest areas is the basic strategy here. Even the fastest ships maneuver sluggishly, and they can't fire constantly. The tactical situation is complicated by each weapons' reliability (phasers always hit but have limited range and damage, while torpedoes sometimes miss their targets) and restricted firing arcs. It's not extraordinarily deep, but there is room to learn.
A lot of the fun comes from the use of the DS touchscreen. You can use the d-pad and buttons to run the whole game, but there's also a complete interface in three tabs for defense, navigation, and offense. You can hail and scan everything in sight, although it's clear that those interactions (as well as warp destinations) are heavily scripted. The developers clearly spent a lot of time mimicking the look of Trek technology, even to the point that it's not always practical. For example, shields and weapons only become fully available at red alert, but there's no real incentive (or consequences) for not immediately going to full alert status, although shields must be lowered for transport. Also, during the unlockable Klingon campaign there's an option for the whole HUD to be in Klingon script--again, it's kind of pointless, but it's a fun and immersive touch.
Likewise, the sounds and graphics are largely faithful to the series--they're not stunning even by DS standards, but they're attractive and the frame rate never drops. Ships do offer dynamic damage to specific components, and they can lose engines if they take hits to the warp nacelles. The music direction deserves particular kudos, since it's semi-dynamic in response to the current alert status and mission parameters.
There's a lot of room for improvement on these strengths, however. Tactical Assault suffers from a few bugs, one which locked the DS up during a mission. It also lacks difficulty settings, and hits a real spike halfway through when players are outnumbered by several waves of attacking ships. The multiplayer is also disappointing: there's multi-card play, but no download option and no WiFi. Assuming that they get a chance to make a sequel, it'd be nice to see online play.