Is Dumbledore as great as he seems?

He is wise and old and learned and kind, but the Principal of Hogwarts is not perfect.  He deceives, he holds back really important information about issues of life and death, and is willing to sacrifice Harry Potter for the good of the many, leading him (as Professor Snape says) “like a pig to slaughter”.  So, is Dumbledore an ethical person?  How flawed are we allowed to be and still be counted as “good”?