There are so many things I want to fix in the build system at work and not enough time.
Christian Reis wrote a good paper contrasting XP and open source.
proofs I think some confusion is caused by the two different meanings that "proof" has in English. One is to "establish beyond all doubt", and the other is "mathematical argument".
I was recently saying that software cannot be established beyond doubt to be correct, in part because we cannot really completely define "correct" for practical programs. You can make an argument that nothing can ever be proved absolutely beyond doubt, only contingently.
On the other hand, raph and graydon correctly point out that formal arguments can be useful in trying to establish confidence, and I certainly agree with that.
I think there is less of a gap between quotidien testing techniques and proof than some people on both sides of the gap might suspect.