I'm a big fan of pair programming. I have used it many times and almost everytime the result was better code that was developed faster. Pair programming is like having continuous code review.
Sadly, there is a lot of controversy with this particular agile/XP practice. Seeing two valuable resources sitting down at one computer makes most managers nervous. They think their team's productivity has just been halved. The worst thing about this mentality is that it makes it clear that the manager thinks programming is just typing.
Mere typing, programming is not. A good idea or a bug caught early on in the process can save a team a lot of work and rework later. By pairing you share valuable knowledge and practices throughout the team, catching more bugs early, and increasing code quality.
