For an explanation of Pair Programming, please visit this wiki entry.
I am pair programming on the ScrumPad project now and the feeling in general is good. I have this perception is the work quality is better than doing alone. Also, the amount of time wasted to find small issues are now much reduced. Overall, its good.
I definitely found the productivity boosted by a factor of 1.5 at least. May be this is specific to my case, as I am working on a mid scale refactoring task. We worked on two user stories so far and completed the stories in 1.5 times faster compared to the individual estimates. We are doing estimation on a regular basis and the variance between estimation and actual hours are less than 5% as we see in the last 17 sprints in this project.
I am yet new to this practice and not in a position to draw a conclusion yet. However, I believe our open space set-up and strong team culture helped us a lot to start this pair programming.
Are you pairing? Please, share your feelings and suggestions.