Concerning Caesar's smile, I think that Ciaran Hinds did it well enough.

I wonder if Caesar himself would be as famous had he not been assassinated in such a tragic way.

In Dante's Inferno, Brutus shares with Cassius and Juda the incredible honour to be in the last section of the ninth circle (I dare say it was well deserved) with those who were guilty of the most hideous of transgressions and betrayed their benefactors...

Of the two others, who head downward are,
  The one who hangs from the black jowl is Brutus;
  See how he writhes himself, and speaks no word.

And the other, who so stalwart seems, is Cassius.
  But night is reascending, and 'tis time
  That we depart, for we have seen the whole.

...while Julius Caesar is only in the purgatory in good company :-)

Plutarch wrote that one day, Caesar said to his friends, after having heard Brutus speak : I know not what this young man wants, but all that he wants he wants very much (Brutus, VI).  He was a brave and energetic young man but an inept politician and not as honorable as that, if we consider his deeds in Cilicia. He was more than a money-lender, he was an usurer.  And very arrogant and stubborn too. Even when he asks me a favor,  writes Cicero to Atticus, there is always something arrogant and churlish: still he moves laughter more than anger. What else could be expected from Cato's nephew ?

If you think that I don't like Brutus, you are right ;-)