The new characters aren't the only departures, as gameplay in Sly 3 seems to change dramatically every few minutes. You'll spend most of your time hopping around and stealing things, as per usual, but the action is regularly broken up with safe-cracking, target-shooting, toy-car-driving, and other minigames.
A few of these get tedious fast, but most are enjoyable enough that they actually feel too short. Still others aren't minigames so much as game parodies, aping the tank action of Vindicators, the giant-climbing of Shadow of the Colossus or the galleon combat of Sid Meier's Pirates! These also get recycled for the game's multiplayer modes, which let players pilot biplanes, ships or computer-generated tanks against each other, or just play cops-and-robbers in a Sly-vs.-Carmelita chase mode. It's no Splinter Cell, but it does give you a reason to play the game after you've finished it.
The whole thing is tied together by the series' unique charm and personality, which haven't lost steam after two sequels. Also, while it's ostensibly a kiddie game, the production values and acting are top notch, and the unique, cel-shaded art style is as compelling as ever. (Although it's less compelling if you use the included red-and-blue 3D glasses, which add little other than a bad case of eyestrain.)