Pros
Opower feels like a Silicon Valley software company in many ways. The company has a unique commitment to doing the right thing and supporting the company mission of saving energy which pulls together a motivated team. The management team is highly approachable and mostly likable. There are some of the perks more likely to be seen in on the west coast such as free snacks and drinks, massage and free lunch one day a week, casual dress code, encouragement to bike to work. The vibe feels like a small company. If you're looking for a software company in the DC area that feels more like something you'd find in the Bay Area, this is it.
Cons
Bureaucracy is high relative to company size with bank-like title inflation. Pace of innovation is slower than you'd expect in SF or NY (though probably fast for DC). Support staff operate as inflexible fiefdoms.