Mindless, easy, fun.
The designing of a handheld RTS has failed numerous times in the DS' history; Heroes of Mana, Shogun Empires and other titles tried but never quite made a fun, standard RTS. Revenant Wings, however, proved that it is possible to have an enjoyable RTS on a handheld.
RW's plot is mediocre and exists solely to keep up the FF XII name. After taking flight on a newlyfound ship, Vaan and friends discover a new continent, with a new species and familiar monsters (aegyls pose as the humes of this continent). One of these aegyl joins the party, and together they fight past hordes of bad guys in an attempt to save the contintent. In a nutshell, there is a divine threat to the aegyl; Vaan's company must destroy the evil beast causing the trouble, etc. etc. etc. — nothing memorable.
All of the controls are touch-screen based; the world map and dialogue bars are the only areas of the game where you aren't required to use your stylus. Using characters as Vaan, Penelo, Balthier, Fran, Ashe, and numerous others from FF XII, the player summons Espers of pre-determined levels to take out any and usually all enemy units deployed on the map. There are exceptions, of course, in some of the many optional quests (though considered optional, they turn out to be quite mandatory when in later levels the difficulty level increases; some of these missions also are required for finding certain characters' Quickenings), but for the most part destroying everything on the map is the main objective.
The Ring of Pacts was an ingenius system and is what made the game noteable; completing certain quests gives the player auracite, which can be used to 'purchase' new Espers in the Ring of Pacts menu. These Espers make up a rock-paper-scissor like gameplay; flying is strong against melee, melee is strong against ranged, and ranged is strong against flying. Using the different leveled Espers throughout the game is fun, and often noting the weakness of opponents is key to winning the battle. These Espers can either automatically be placed in the match or can be summoned via summon gates (which can be captured by heroes). There are a ton of Espers you will recognize from previous games and even semi-deities like Ifrit, Ramuh, Shiva, etc..
RW's gameplay is clean, and Square Enix did their best to allow the player to select a single unit in a crowd; they did a decent job, and though a lot of the earlier missions of Revenant Wings come down to simply selecting all units (x) and attacking, later levels require strategy, attention, and hero's spells. Only 5 heroes can be selected in a mission, but all get at least a little experience from every battle.
The graphics are cute, innocent, and are about as captivating as the storyline. The in-game graphics can get pixelly during in-game cutscenes, but these are made up for in the graphically-astounding scenes during occasional parts of the game. It's Square Enix -- we expect no less.
Overall, a decent game to add to your handheld collection. If you're looking for a challenge or a sentimental storyline, I wouldn't suggest a purchase, but if you just want an enjoyable handheld RTS, Revevant Wings is the only option available -- a viable option at that.