What advantages/disadvantages have you seen with Pair Programming in the classroom Many of us use or have used Pair Programming in the classroom. 

See https://www.agilealliance.org/glossary/pairing for a discussion if you like. 

@BennettBrown has pointed to research showing its advantages, but not all users may have had positive experiences. 

If you have tried it, what have you experienced both on the positive side and the negative side. 

Perhaps more important is what else do you need to do in structuring your course to make up for any disadvantages or support any advantages. These might involve ensuring fairness in sharing work or in grading. 

I tend to use it at every level, but there may be issues you see in various courses. 



The answers seem to indicate a fair amount of misunderstanding of Pair Programming. It is not just two people assigned to a task. That can lead to division of labor, which often fails. If two people just divide up the work and do it unwisely, they have the additional task of integrating their work which can be very difficult. Neither is it one person just working and the other just "reviewing". It is a much more cooperative endeavor. 

If you want to really understand Pair Programming, the book Pair Programming Illuminated is a great place to start. If you want to see Pairing integrated into a complete Agile Programming workflow of a small team, Extreme Programming Explained is good. I actually prefer the first edition if you can find it.
I give 11 lab assignments in CS 1, and I assign partners for the first four or five so that students get to know each other, and then I let them choose their partners, or choose to work alone.  I try to discourage them from working alone, but some students just don't want to deal with people, and I feel bad forcing them.  (I also give six projects, worth more collectively than the 11 labs are, and they must work on these separately.)

This is all anecdotal, because I only teach one section of CS 1 a semester, but: I don't see any patterns.  Some more socially awkward students find the right partner and have lots of success building skills and confidence during the semester, whereas others don't, and struggle alone for the rest of the semester.  Frequently, students who come in with previous knowledge (say, those taking the class the second time) will ignore their partners, or do the work and hand them the answer; but others seem to have the "teaching gene" and almost act like TAs for me with the weaker students.  It depends a lot on who the students are, and how lucky I get when I pair them up.

I do give each student a questionnaire the first day, so that I can try to match up the students with similar experience, or students that have already passed Calc I, or something, but (again, based on anecdotal data with a very small $n$) none of these seems to have much of an effect.

I'll be watching this discussion to see if anyone has done a lot of research on who to match up with whom, because I haven't figured it out yet.