I think in general Peer reviews are a very good part of development process, they often catch or question things which were not apparent when code was originally written and make you more self conscious so you format better, put in comments etc.
However if you are pair programming you effectively have a live peer review, so is it worth still having a peer review as part of the process? Can you have pair peer reviews?
I ask as pair programming is starting to happen where I work, and generally this is seen as a substitute for peer review. I am not so sure, but think that the developer time spent pair programming and peer reviewing may damage productivity.
There was a similar question a while back but with different emphasis and no clear consensus
That depends.
The goal of a peer review, in my opinion, is not only to find defects directly to the code written but to make sure that the code will also work well with the exist code base. Sometimes, you may want to involve an expert of the code you are writing and it may not be a member of the pair.
For example, if your write the 3D Graphics part of an application, you may want to have it reviewed by your OpenGL expert.
So depending on the circumstances, you may want a third pair of eyes to look at your issue. This person may not even be collocated (in another time zone or something).
Plus, when you pair, you may have a tendency to think alike. Therefore, another opinion may open your eyes on something you missed.
If my developers pair to code, I would still incite them to have their code reviewed if they are not 100% expert in that part of the code.