Whether or not you'll enjoy this game depends almost entirely on viewing the cover. If you see "Dynasty Warriors" and "Gundam" paired together and immediately scream in glee, this is the perfect game for you. Otherwise, be cautious.
Honestly, there's a lot to hate about this game. The combat consists entirely of mashing buttons to take down hordes of generic enemies that are actually the same 2-3 bad guys repeated endlessly, punctuated by the occasional boss. Boss fights are hampered by the massive amount of juggling inherent to the combo system- either you spend the entire battle wailing on the enemy, or they start a combo, and you can only watch helplessly as they continue hitting until their combo ends. Combat is further hampered because health items drop entirely randomly, so if you're unlucky enough to get tagged with damage at any point you'll spend minutes hunting the map for item boxes and praying you get the right item. The graphics are serviceable, but don't really scream "next-gen".
For all the minuses this game presents, there's a plus that might outweigh it. The biggest is the inclusion of many great Gundams to play as- you can play famous mobile suits from Amuro's RX-78-2 (Mobile Suit Gundam) to Heero's Wing Zero (Gundam Wing)- I was especially pleased by the inclusion of Zech Marquise in Gundam Epyon (Gundam Wing). Game modes don't go online or present anything terribly original, but there's the usual Warrior-esque Story/Campaign, and a couple of extra fighting modes for a bit of variety mostly designed around battling versus friends. There's even a very small RPG aspect, where you collect various components during the story to upgrade your Gundam.
Overall, this is a fun little hack-and-slash game built for a very specific audience. If you're someone in that audience, then this is a very solid title that I highly recommend. If you're not in that audience, this game will be merely a generic hack-and-slash title for you.