I think the original plans, and maybe even some footage shot for that scene, had Dooku using two lightsabers at one point (Obi-Wan's? Though it doesn't look like it in that shot). I forget if it was supposedly in the Anakin duel (probably), or the Yoda one.
A lot of people were hoping some of this scene would be included in the Deleted Scenes feature of the DVD, or on Hyperspace, or something. But unfortunately, it's yet to happen... Just a few stills here and there is all so far.
Very intriguing though!