Pros
Valve’s flat structure and relatively limited bureaucracy really unlocks your ability to produce. If you are a multi-talented individual who can run a million miles per hour and are tired of other people getting in your way, Valve is probably the most productive environment you will ever see. Compensation can be excellent and the perks (annual paid vacation, laundry service, personal training for self and spouse, great office views) are wonderful. You can work with the smartest people in the world at Valve and just sit down for lunch with them whenever you want, and learn a ton about everything from hardware manufacturing to software engineering to network operations at scale.
Cons
Flat structure really means an informal power and influence hierarchy, so you have to be socially adept or you will get blindsided repeatedly. Some employees are more equal than others and are the ears and mouthpieces of board members. Cash compensation can be average or below average for people with solid but not exceptional skills. Company leadership is allergic to the word “policy”. Libertarian to the extreme - unwilling to even agree on matching basic humanitarian charity contributions, lots of “both sides” arguments in debates about online behavior. Being a jerk or worse to your coworkers is largely tolerated because the leadership does not place any value on “being nice”. Tiny HR department tries but they are necessarily subservient to the leadership, and at the highest levels, the company doesn’t believe that HR should get involved in anything except hiring, benefits, and logistics. If Gabe takes a personal interest in your area, you could find yourself suddenly overruled in ways that feel surprising and whiplash-inducing given the otherwise autonomous nature of employment at Valve.