I think you're right. It is a very lengthy blade twirly show-fight which is fought at a constant frantically high speed. The one thing that doesn't make it boring is the awesome stage were the fighting is set (I was really in awe how beautifully they managed to bring the planet of Mustafaar to life). Actually the part were they just whirl around the blades made me laugh - because it reminded me more of a scene you'd expect in a film like spaceballs.

I missed Vader using his telekinetic abilities. I missed Vader utilizing his force choke. And above all - like you said - I miss the logical next development step in the fighting style of both combatants (I thought we kinda witnessed such a milestone with the Anakin vs. Dooku fight in AOTC). Alas, that was thrown overboard (as was the 'narrowing down' of the number of designs in vehicles and uniforms to take a strong step towards the minimalism of the classic movies).

P.S.: When you compare this swordfight to the Obi-Wan & Qui-Gon vs. Maul fight, you really begin to doubt Nick Gillard really had the same amount of creative freedom in ROTS that he must have had in TPM.