John De, President of N-Brain, has to say this about pairing:

… I discovered that two heads really are better than one. Developers have different ways of interpreting code, and different ways of solving problems. Combining this rich diversity creates a strength unequaled by any single developer. Put me in a room with a junior programmer, and turn us loose on some task, and I guarantee you that I will gain new insight into the problem from this developer, and that our resulting solution will be stronger than anything I could have come up with alone.

Read full interview here: http://java.dzone.com/news/interview-john-de-goes-free-un.