What I know about Ney, is that he was a skilled commander, who's temper sometimes ruined his coordination with other forces. It's seemed like he just wanted to beat the enemy so bad, that he didn't always had time to wait for the right moment of attack.
During the retreat from Moscow, he performed excellent, but Napoleon thought he died. When Napoleon found out that he had survived, he said: "Surely, this man is the bravest of the brave"
After Napoleons exile to Elba, Ney served the King, and he was even the man send out to stop Napoleon from returning. Ney shifted sides though, going back to his old master whom he loved. This caused him to be excecuted after Napoleons final defeat.
Ney performed with aggression (Too much) and bravery as always, in the battle of Waterloo, in which he at some point was found beating an English cannon with his sword in frustration over the way the battle was going.
Murat was a Cavalryman, and a damn good one, but too abitious. His wife, who was also Napoleons sister, plotted with him far too often. When Napoleon was thought dead in Spain (He was actually pushing the English out of the Peninsulla) Murat was thought as the man who should replace the Emperor, something that was against Napoleons whishes and therefore treachery.
Napoleon forgave him though. He probably needed him, and even made him King of Naples. Murat ended up abandoning Napoleon when things were looking grim in 1813. I think he asked to be forgiven and serve again in "The 100 days" But Napoleon could not forget his doubble treachery, and wouldn't have it.
Davout, I cannot tell you much about, but Im sure Hudson can
