Pros
This is a great place, with very smart people doing a great thing for a great purpose, to save our planet. That's the best thing about Opower is the people and the capability to learn as many new technologies as your brain can hold, and even more fun is applying that learning to solving very complex problems. It's results that matter here, so it makes it pretty straightforward. The people make the work fun. I highly recommend Opower as a career move you will not regret!
Cons
Middle management has a lack of people skills, and because of that people's careers can seem at a standstill. It's very much an "up to you" kind of place, so you have to toot your own horn, make sure you get recognized and appreciated. Everyone including the managers are so heads down and getting things done they can overlook good contributions by others. Also it's getting a bit political as change occurs and people start carving out fiefdoms. The good thing about that is it's not done haphazardly, the bad thing is that it may come as a surprise to many as the changes occurs. More engagement with employees would be a good thing to settle any nervous reactions.