Soooooooooo....
Tarkin is making an appearance? An OT character that certainly makes sense.
He calls Darth Vader his friend. He knows and acknolwedges the Jedi in Vader. He doesn't fear Vader and actually seemed to hold rank over him to some degree.
Tarkin (and Peter Cushing to be more precise) is a favorite of mine. I have always loved his character because he's the embodiment of the Empire to me. Even moreso than Vader of the Emperor.
Tarkin is the power-hungry. He's the every-man who is willing to kill for this new way of life he envisions for the galaxy. He's the kind of guy who looks at the Empire as serving his own ideals though, as it makes people like him have an avenue that they wouldn't have had under any legitimate democracy. He's ruthless and cold, like the weapons of the Empire. He's distinctly British and we all know that equates pure evil.

He's not all-powerful, but his posture is as though he is as dark and evil as any force-wielder. He's the career soldier who sees opportunity to make himself stand out in the eyes of his superiors in a time of chaos.
Tarkin, to me, is the prototype for Grand Admiral Thrawn's character... I like the pure humanity gone awry aspect of them, and that he's just a person, nothing special other than maybe his intelligence, tactical ability, personality, etc. It's always how I envisioned the Empire. Not as Clones, but more like the average people taking advantage of the times they live in to institute their ideals.
The Clones were merely a tool to get there... Once the war ended and the political landscape changed drastically, then the true evil oozed out of the galaxy and Tarkin was the worst of them. It's very similar to history at various points, and so I've always felt Tarkin had that special tie to human history that made the OT so special.
I love seeing that they're going to delve into a character's backstory that makes sense though. I just hope they do it justice. Cushing really made Tarkin evil through his acting, and I'd hate to see The Clone Wars diminish the character in any way.