I've only had the chance to visit once, but it's wonderful! The best news I've heard is that (i seem to remember) 80% of people that live in slums (slums all over the world), only live there for 1 generation. That means in 80% of cases, people get out of the deepest poverty (people usually come to slums from rural areas, so slums don't shrink). The world is getting better, but it does take a LONG time.
http://www.ted.com/talks/hans_rosling_the_good_news_of_the_d...