Although I like some of Oscar Niemeyer's work overall I am not a huge fan. Unfortunetly in Brazil, specially in Brasilia, criticizing the man is often taken as an insult to the country itself. This obviously hinders objective analysis concerning his work. This is why articles like this one, written by someone who I imagine is not influenced by such an atmosphere is useful.
The author of the post is Edward Winkleman and he uses Niemeyer's desire to alter some of his buildings to discuss if an artist should tinker with work which has been presented to the public. He also talks about some of Niemeyer's creations here in Brasilia which have seen changes and gives a before and after critique.
Here is a slide show of some of the constructions mentioned in Winkleman's post.