If you are a die-hard fan of the show with some cash to spend, then you might want to consider picking this game up.
What is great about this game? The battles. Just like in the series, the battles are fast, and you need to be fast to survive. Just mindlessly slashing with your melee weapon won't get you anywhere. You have both the melee and ranged weapons, as well as a charged up version of those. You can also perform a special combo by hitting the touch screen after filling up a bar (or two), then finishing a melee combo. There is also an ability to block by hitting the button for melee and long ranged attacks at the same type.
While it is great and all, there is also the balancing problem. Virtue is way to unbalanced with his cannon. While there is a need to reload the long ranged weapon (which you can reload without limit), there is no need to reload with charged range weapon. That said, as Virtue, you can fire away with his GN Bazooka and easily wipe through everything. On the other side of the spectrum, everybody else's ranged attacks seem to be pretty useless. Except for Dynames sniper, every ranged attack is easily dodged by the AI, and even the sniper won't be doing much if the target doesn't decide to stop and shoot at you. You are probably going to find your Exia damaged a lot since his ranged attack is too weak to the point that it might even be detrimental to hit the A button at all. The developers even made the game so that you have to stop and pull out/put back your sword/shield everytime you decide to use the other weapon.
The diversity in the game is huge. Different factions fight differently and so do the Gundams. Exia (as told before) is a fast melee utilizer, which apparently goes great against the ranged AEU and it's missile launchers. Kyrios does great against the slower HRL by utilizing it's maneuverability (and also, you CAN transform into the fighter by hitting the buttons for ascend and descend simultaneously. You get access to his bombs and laser). Dynames is great as a ranged shooter (with it's trademark sniper) and is great taking out the Flags before they start circling you like a shark in the sea. Virtue (with it's +9001 ultimate elite doom cannon of ultimate destruction and desolation a.k.a. GN Bazooka) is great against all of the factions.
Missions are probably what would keep you sucked into this game, and unfortunately, they also have fault. While they do feature destructible buildings and plenty of bosses with familiar faces, they also feature the same goal. Kill X before they reach A, Kill X or whatever random mobile suits, Kill X in a certain time limit. The AI is smart, and is capable of flanking you and attack you from your blindspot. However, the stage is so small and claustrophobic that they will probably succeed when they attack your blindspot because you ran into an invisible wall and couldn't move out of the way in time. Dodging missiles also do not feel fun when they are small objects displayed on a small screen, and you don't see them until you've been hit. Of course, you can get use to this, but the fact is, you shouldn't have to.
After a mission, the damage the Gundam sustained is going to carry over. There are also multiple missions you can choose from (or one urgent mission). All in all, not a lot of things to do except for grinding those missions.
If you understand only English (and watched all the English subs for season one), then you probably won't have any problem going through the menus. SAVE, LOAD, YES, NO, NEW GAME. If you can read that (which if you can't, I have no idea how you read this), then you are ready to play. You won't understand what the hell the characters are talking about, but if you watched the anime, then you probably won't care unless you are a die hard fan. The mission goal is, extremely easy to decipher after one or two missions. They play a short cutscene of an object, and you either kill it or (rarely) defend it. If there isn't healthbar of the object on the bottom of the screen, then it is obviously friendly and you have to defend it. If not, go and kill it. Your targets are also conveniently marked out in special HUD items. Obviously, not knowing Japanese should be no barrier for this game if all you want is Gundam action.
So is it worth it? You decide. Being the only Gundam 00 game out on the market, die hard fans with cash to spare (around $50... that's right, full price for a DS game. You better have a lot of cash to spare to buy this expensive one) should pick this up, as who knows if they are going to bring this one to the states.