The best Ratchet & Clank experience to date.
For the third time in the series, the gameplay is very tight. Both Ratchet and Clank move well, and the camera, over which the player has total control, never encounters any difficulties. The weapons all aim well, and most of them can be upgraded to include a lock-on mechanism. In addition, there are a couple of vehicles you can use, both on land and in the air. Although these vehicles don't control as well as the rest of the game, they're still fun to use and provide a different feel to combat.
The weaponry in UYA is possibly the most impressive of any game ever made. Not only is it possible to use a few weapons from the first two games, but the new creations include a couple of the most imaginative arms to date. The Infector causes enemies to attack each other, the Spitting Hydra is capable of locking onto multiple enemies at once, and the Rift Inducer creates small black holes which suck up anything that gets too close. The weapon leveling system from Going Commando has been expanded, allowing upgrades to weapons from the first two games that weren't available previously, and generally providing more replay value.
Like the original R&C, UYA presents character dynamics that were absent from the first sequel. This is achieved through highly expressive facial animations, clever dialogue, and the series's typically superb voice acting. This game also presents a new style of narration for the franchise, whereby interactive comics tell the story of superhero Captain Quark's past battles against robotic antagonist Dr. Nefarious.
In addition to the above, Insomniac has added, as they always do, little details that provide some flavour to make the game a bit more interesting. There are more paint jobs for your ship than ever before, and collecting enough hidden titanium bolts allows you to buy different skins for Ratchet. While those details could have been left out altogether, their inclusion demonstrates the developers' love of games, which is present throughout.
If you have to play only one game in the R&C series, make it UYA. That being said, this game owes a lot to its prequels. If you liked the characters in the original, and you liked the weapons in the second game, then you'll probably love UYA.