Is the result better than with careful code reviews [of the critical pieces] (both after writing, but also short checks during development over a code listing and coffee)?
Intuitively, everything with coffee involved ought to be better! :-)
Better than some theoretically perfect practice of careful code reviews? I don't know. Better than code reviews as actually implemented everywhere I've worked? Yes. (In particular I find it's really hard to maintain the discipline of carefully going through each other's code when you know that most of the time you won't find anything)
That being said, I do miss solo work, because I could get into the zone, and even if I was going down the wrong path, it was ME doing it, master of my own domain. It feels like I'm alone on my boat sailing into uncharted waters, an adventure.
At its best, pairing feels like being part of a tactical response team, at its worst: like there is a machine that turns my brain cycles into money, and they let me keep some of the money at the end.
Edit: Rereading both comments, apparently pairing makes me wax with metaphors, like a... nah