my thoughs are the accomplice is the Mirialan jedi talking to ashoka. or she could be working with sidious. not sure about ventress though, would be cool if shes back .
At first I suspected Sidious, but then the lightsaber cuts convinced me it was Ventress. But why? If it is Ventress was she targeting Ashoka all along? Did she pose as a Jedi or does she have an accomplice? And how did she know that Ashoka would get arrested? Most of all I want to know what Ventress' motives are, I mean I never got the feeling she hated the Jedi, or Anakin - although they do have a history...
But yeah, the chase scene was awesome and suspenseful. And I thought the stun bolts deflecting off her lightsaber was visually stunning. I also like the Imperial theme going on here, what with the Imperial March, the prison cells from the Death Star and the fact that there are battlecruisers, tanks and military prisons dotted about Coruscant. Can't wait to see what the underworld is like. Great episode.
EDIT: One thing I noticed has improved is the animation of facial expressions, its sort of subtle but you'll notice they're far more expressive and detailed, same goes for gestures etc. TCW has certainly come a long way.