Programming is one of the few professions where one can be very successful as an introvert, working in a manner that is compatible with my personality type. I think it's great that there are other methodologies for people with different preferences but I hope pair programming doesn't start to be seen as a "best practice" that is forced on all teams without acknowledging these personality differences.
In a way I think it is a "best practice": It's a pretty central part of "Extreme Programming", which was one of the early sparks that ignited the whole "Agile" movement. And from what little I've gotten to do it, it really is an effective way to code, so I'm all for it... But yeah, I'm probably pretty extrovert, so easy for me to say.
I don't know how, exactly, but it seems to me finding some way to get this to work also for the more introvert among us should be a pretty high priority on the methodology front.