While I have no idea whether Mr Gates' motivations are altruistic or not, I would of course give him the benefit of the doubt and presume he has good intentions. After all, though I view Microsoft as 'teh evil' in their business practices they have also done some good work in so called 'progressive employment practices' notably by including sexuality in its discimination policies.
Having said that, every pound or dollar in Microsofts or the Gates foundation's pocket is a pound not in someone elses pocket. However good their intentions, what reasoning leads anyone to believe that they are more capable of making use of that money than anyone else in the world. Most governments have good intentions, considering the harm they are prone to do why would anyone be so ready to trust someone with far less accountability. To sum up my point, to pursue huge amounts of money and then split it up between what you think are good causes, is at best an authoritarian 'I know better than you because I am more powerful than you' attitude and far less worthy of praise than spending all that time making money in actually helping people.
You ask Charles for citations, while I suspect those most effected by the foundations work aren't in a great position to be publicising the experience.. some journalists have tried to look beyond the aims of the foundation to the actual effects they have. Just focusing on the effects of the fund:
Also note, the article in the seattle times is followed by a decision of the foundation to cancel the review in its investment policy.
None of these articles explore the wider impact of how the money was gained in the first place and whether any good work done can wash away the stain of Microsoft's name, as seen by those who don't view making money at any cost as a benign goal.
Lastly, in case anyone misunderstands me, no I am not an Apple fanboy and have no more faith in Steve Jobs than I do in Bill Gates.