It's like a lot of people say, he may have given away a LOT of money to charities over his career, but the amount he's given is marginal considering his income and wealth. It makes as much an impact on him as us giving $1 would.
That's not to say it's not incredibly generous though, because it still makes a HUGE impact on the charities that receive it, who are used to receiving donations <$10
Over $100 billion is marginal to him? Thats more than his entire net worth today. Think about all the money you save for the next 50 years, all the assets you build (house, cars, business, etc.) and then just giving away 3/5 of ALL of that. That would be marginal to you?
He really is a good guy considering the fact that those organizations would be billions of dollars lesser. Also, Bill Gates has just kinda jumped into the spotlight after Steve Jobs' death. No one paid attention to his donations and auch before Steve Jobs died and now he's huge.
That's not to say it's not incredibly generous though, because it still makes a HUGE impact on the charities that receive it, who are used to receiving donations <$10