Starcraft lite, but not as lite as you might imagine.
Two factions with their own strengths and weaknesses, and many troop/vehicle types. Bargain pricetag.
The bad:
Only twelve missions per faction. Basic turtling-up strategy wins nearly every time. Zero story, other than "aliens versus humans, go get 'em!".
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Real-time strategy games are notoriously difficult to translate onto a handheld, as evidenced by the many failures to do so (with the sole recent exception from FF). One has to wonder why, then, any development company might want to take on the task of trying to do a Command & Conquer clone for the DS? Well, luckily, Cypron Studios and Destination Software have come through with a decently implemented RTS in the thinly-veiled C&C clone, Command & Destroy. If you like Starcraft or C&C's style of play, you will probably like this one as well, since it involves many of the same features and gameplay options: build up a base, put in some defenses, tap into the land's resources to expand, build an army, and wipe out the enemy.
The two factions play differently enough that you don't tire of the gameplay that quickly. The human faction has all the old types of gear and troops you are familiar with (tanks, missile launchers, helicoptors, and so on), encouraging the player to take out the enemy with brute force. The alien faction is more mind-based, akin to Starcraft's Protoss, in that the vehicles and troops are much easier to kill, but the use of mind powers enable, for example, your troops to convert enemy tanks or men to your side. It involves a slightly different strategy from the humans, but ends up being different enough that you don't feel like like you are just re-playing the human campaign with different-shaped units that do the same things.
The strongest thing about the game is the gameplay itself. Using the stylus as a mouse, one can click on whatever one wants to control, and a menu pops up with available options. Or, by double-clicking a troop, it will cause all identical troops to also be selected. Finally, one can drag a box over a group and take control of them all at once. In other words, the ability to get something on the screen to do what you want it to do is relatively simple and smooth. I never felt like I was out of control of what was happening, and could quickly respond to any emergencies or events that unfolded on the battlefield with ease. Another strong point was that the enemy seemed quick to exploit any weaknesses in my base defenses, homing in on any unprotected buildings and decimating me if I wasn't careful.
The biggest gripes I have about the game are twofold:
1) The entire set of human missions, and most of the alien missions, can be won by simply building some defense turrets around your buildings, and massing an army to send out to decimate the enemy. There is little reason to ever try chipping away at the enemy, since that stratgey effectively seems to activate their aggressive side, and you are suddenly inundated with wave after wave of tanks. So, if you don't like turtling up, you may find this a bit tedious about halfway through the human missions.
2) The game is far too short. I finished the dozen human missions in one evening's worth of play, and the alien missions in a couple more (it took a little longer to figure out a winning strategy). In other words, the game ends within two days. I guess that's what you get when the dsitributing company is more interested in selling you a vacation than a video game (try clicking Destination's link to see what I mean).
In the end, though, if you are craving a Command & Conquer style RTS on your commutes to work, you could do worse than Command & Destroy, at least for the few days it'll take for you to finish.