The Holy Goat of Power wrote:

Note: You do not know what your enemy will be when you deply and don't find out until you first make contact. This keeps you on your toes because while a tight formation of marines out in the open is great -even necessary- when fighting the spawn, it's certain death against the missile-shooting machina. Every race has several Elite league champions who favor them. I've run into nothing in my own experience to suggest any balance problems.

Laser Marines are the titular human side. They resemble a cross between imperial storm troopers and the stay-puff marshmallow man. Their advantage is highly mobile units who excel at long-range combat. Their disadvantage is being the most frail race. They're probably the most tactically versatile of all the races

Machina are the killer robots. They're bronze and kinda look like the big brute robots from attack of the clones. Their advantage is having the most highly specialized units, the best battlefield intelligence, and on average the most durable units. Their disadvantage is also having the most highly-specialized units, which can destroy their whole strategy if a couple key units are destroyed. They tend to win by slowly taking control of the whole map and trapping their enemies.

The Spawn are the Xenomorphs. While the queen is pretty nasty looking, the rest of their units are silly looking combinations of human limbs and maggot bodies. Their advantage is having on average the fastest units and, if they can manage to secure an area after a skirmish long enough for the queen to get there, expendible units. Their disadvantage is an almost total reliance on up-close bite attacks. Their best strategy is to use stealth before launching the mother of all "They're coming out of the goddamn walls!" ambushes.

Greys are the anal-probing aliens. They look like sectoids from X-Com. Their advantage is having neeto space-age technology like personal deflector shields and cloaking devices and Warp guns whose projectiles can turn corners and the most badass vehicle in the game. Their disadvantage is their weapons and deflector shields use the same power supply, so they can't handle extended combat. They tend to win by doing hit-and-fade attacks using their saucer to transport energy to and from the HQ.

Single Player:

Missions are puzzle-based and highly scripted. The player has full control over their deployment but usually are at a positional and force-point disadvantage. A good tutorial at easy difficulty and a decent "how would YOU crack this hardened fortress?" challenge at medium/hard, but by no means a substitute for multiplayer.

Problems:

The non-game interface is absolutely bare-bones. There is no way to preview maps before playing. You need to manually provide the numbers when doing any out-of-the-ordinary game management. Once you're in a game, you can't get back to the main menu without restarting the program. If you're running in fullscreen, the only way to close a game-in-progress is Alt-F4.

The Money issue:

I am unaware if any other multiplayer tactical game with this game's ease-of-orders or unit balance exists.