Yoda and a squad of clones rushes to meet with the Toydarian royalty in order to negotiate passage for supply lines, but are ambushed by the Separatists.
Right from the beginning, the scale of this episode is astonishing. A massive (albeit short) space battle kicks off the story, perfectly capturing the Star Wars feel. Also, it's neat to see Toydarians other than Watto. I like how TCW is expanding the Star Wars world we already know.
"Smaller in number are we, but greater in mind," says Yoda. This is the moral crux of the episode. The battle droids are stupid and lifeless, but Yoda and the clones are intelligent living beings connected to the Force. It's a good moral, but the problem is that it's hammered home far too strongly. The battle droids have never been more stupid than they are here, and it's painful. It's impossible for the villains in a story to be a credible threat when they're so moronic that they literally kill each other by accident. Fortunately, the other side of the story, with Yoda and the clones, is far more compelling. We're told by Yoda that the clones are actual individuals within the Force—they have souls, essentially—which is a very important detail. Given that this is the first episode of The Clone Wars, it's fitting that here we establish that the clones are actual people, not cannon fodder like the droids.
Yoda's character in this episode is near-perfect. He acted like the Empire Strikes Back Yoda that we all love, rather than the rubber jumping frog from the prequels.
The best part of the episode, however, was the music. "Yoda's Theme" (arguably one of the best musical pieces in the entire saga) permeated the episode, as well it should. It's ridiculous how the theme was almost never used in the prequel films, and the fact that it exists here is absolutely wonderful.
The action in the episode varies. Every action scene leading up to the big confrontation in the canyon is childish nonsense, but that big battle is incredibly well-done. "Lopsided" is how I would describe the action in "Ambush," as with the episode as a whole. On one hand, the characterization of Yoda and the clones is awesome, but conversely, the droids (and most of the action they're involved in) are so terrible that they drag the entire story down with them.
All in all, this episode ends up being pretty decent. Not amazing, but definitely leaning on the side of rather enjoyable.