Is Antony's estimation of Brutus accurate at the end of Julius Caesar?and do you think the sentiments are Shakespears or really Antony's?
Yes, they are accurate. Antony calls Brutus, "The noblest Roman of them all" (line 68). Brutus stayed consistent to his values throughout the book. He was the only character whose actions never contradicted his words.
A better way to phrase the question is if Antony really meant what he said or if that is Shakespeare's commentary. It certainly contradicts what Antony said about Brutus and the other conspirators in Act III, scene I when he refers to them as butchers and says they will be cursed from here on out. He also had harsh things to say specifically about Brutus, as his whole speech was designed to show Brutus is not the honorable man he would like people to believe. However, these things were said in the heat of the moment and done for the purpose of getting people on his side to go after the conspirators. Perhaps, after getting a chance to think about why Brutus acted the way he did, he realized that Brutus only did what he felt was right.