My problem with pair programming is that it doesn't allow me to get in the mental state of "flow". The most productive state at least for me is when, for a period of time, I'm so focused on the job at hand, that I'm not aware of my surrounding. This is where my most productive work happens. You're completely immersed and focused.
When pairing I never can get into that state because I keep getting interrupted with "name that method x", "move that method before that method", "refactor now". It really breaks my focus.
I find it useful when tracking obscure bugs, where you can bounce ideas off of someone and basically nail the problem faster.
I've found that when I'm in the backseat we can be most productive as a pair if I spend my time trying to keep the driver in flow. When I first tried pairing the programmer control freak in me made this very difficult. I was effectively trying to write code by commanding someone else's hands to do what I was thinking.
By focusing on keeping the driver in flow you begin to appreciate when it's better to shut up and let them get on with writing the code, accepting that people have different coding styles is important here. You can then use your attention to either help out when they get stuck or maybe to tell them what the next test should be.
When pairing I never can get into that state because I keep getting interrupted with "name that method x", "move that method before that method", "refactor now". It really breaks my focus.
I find it useful when tracking obscure bugs, where you can bounce ideas off of someone and basically nail the problem faster.