Originally posted by Rampant ox
But in terms of duelling his speed is severely impaired. He has to rely on brute strength to win a lightsaber fight. Knowing his old weaknesses etc are besides the point - due to the limitations of his suit there is nothing e can do to fix them.

It would be a good idea to read this i ripped out of wookie and i can prove to you its true, remember in jedi academy when jaden stumbled into vaders training room with droids? this is the one down here

Around 3.5 ABY, Vader had ordered ASP-19 droids, lightsaber combat droids based off the ASP-series droid, produced to fight him in sparring matches. They were faster and stronger than an ordinary man, and programmed with the knowledge of a hundred sword masters and a dozen fighting styles. Vader defeated them time and again, and ordered a new, improved batch of them. As his finesse improved they became too easy to defeat, even in a two-on-one match.

Originally posted by jollyjim311
It's far from irrelevant. It at least helps Vader's case more than Dookus. And Vader is different in the regard that he is more level headed, has a more powerful grip of the dark side, has armor that would be helpful against Makashi, has much more physical strength and uses it in his fighting style, and knows more (Vader is a mystery of capabilities to Dooku, while I'm sure Vader remembers perfectly well what Dooku can do), basically, he has grown in overall power (ANH Novel), but changed. These changes, however, all seem to be in ways that would help against Dooku, more than hinder. The only potential problem is the decrease in mobility, but, this is usually over exaggerated, because his powerful style is basically a hold-your-ground type of fighting, which may make it seem like he is not manuverable, and, has been shown that when he needs to, he can be very agile (lots of novels and comics, like Purge, RODV, and especially Crimson Empire). Another potential problem is the force lightning, but, a saber can block it easily enough.
And lets not forget that according to palpatine the smartest guy in SW, told himself that vaders limitation of his potential is indeed mental,psycological and not physical. And he even told himself "sith power resides in the will not flesh" and Darth sion has proven this to us, he was alive and became powerful due to his will