As a counterpoint to most of the comments here: I work at a company where almost every developer pairs all the time. I absolutely love it. I thought I would hate it. I'm an introvert. I previously worked as a solo freelancer and then as a remote teammate. So I was very nervous about this aspect of the job, but figured I'd give it a shot (other things about the job were appealing enough that I was willing to try it out).

Some thoughts based on my own personal experience:

* The biggest win for me is I am much more focused and productive throughout the day. Having an actual person to be accountable to on a continual basis keeps me from meandering down unimportant rabbit holes, unnecessary/premature refactoring or re-organizing, and general procrastinating (reddit, HN, etc)

* Development is definitely at a slower pace on a daily basis than what I'm used to working on my own, but over time I think it evens out in terms of quality of code and maintainability.

* Knowledge sharing is huge -- when I was solo, I could never truly take a vacation because I was the only one responsible for my piece of work. Now I'm on a team where we all pair with each other and switch around every day... if someone is out, it's no big deal. Also makes it much easier to onboard new people (the company I work at is a consultancy so projects are always ending and new ones beginning).

* Despite being an introvert, I feel no more "drained" of energy at the end of the day than I ever did at any other job. One-on-one interactions with people I know and build trust with just doesn't affect me the way other social interactions do.

* Pairing is not a panacea. Some of the comments I've seen here are about how horrible it would be to pair and feel judged all the time or one personality overriding the other... I suppose that's possible but it doesn't happen at my job because my company values and encourages trust. My team is comprised of mature people who all value team cohesion and working together towards a goal over having to be right all the time or proving to someone that we're better or whatever.

* I am never "stuck" pairing with just 1 person for a long time... we switch around every day. I probably pair with any given person only once per week (on a team with 6 developers). But each team has autonomy to structure the pair switching however they want.

Those are just some thoughts off the top of my head. Happy to answer any questions anyone may have (and if it sounds interesting to you, my company is always hiring... we have physical offices around the world, as well as a "virtual office" for remote employees).