Only once Anakin had attacked Windu did Sidious reveal the true extent of his power - it had been a feint all along. Had he been in as bad a shape as he looked, Windu would
have killed him. And, as soon as Anakin attacked Windu, he unleashed his rage, which saw Windu off for good (and please, Windu fanboys, don't start spouting theories that he's still alive).
Now, when he fought Yoda, I believe that was Sidious at his full potential, and he was just about a match for Yoda, both in saber combat and force ability, and neither held back - there was no reason to. The fate of the galaxy was going to be decided there and then. Had Yoda won, the Republic would have been saved - Vader would be no match for the Grand Master of the Order.
Vader may have assaulted the Jedi Temple, and killed many, but he had two things in his favor there:
1. He had a legion of stormtroopers with him
2. Most of the Jedi in the temple were Padawans, as most of the Knights and Masters were fighting the war. They would have been no match for a battle hardened Jedi Knight who had slain a Sith Lord.
And the reason Vader was so easily able to defeat the Order's battle master, Cin Drallig, was because, if you look in the security recording, he was using Drallig's apprentice as a shield, forcing Drallig to hold back, rather than harm his padawan.
I kind of went off on a tangent there... but oh well