Pros
Bloom Energy has a lot of hype in the cleantech space and you ca leverage that into making connections and finding a better job. People will be impressed that you work there. The main (and one of the few) strengths of this company is the media spin and public image they project.
Cons
You will be expected to work long hours (12+/day) regularly with little recognition for your efforts. A desire to work less will be viewed as you being "not a team player" and you will be looked down upon. The company pretends to be a "startup" but does not care about you as an employee, the work environment is not enjoyable. The company has dozens of VPs (i.e. 1 VP per 20 lower level employees) and even more Directors. Unless you are in this upper class it is extremely unlikely you will advance and will have to navigate a political minefield of everyone else (including your manager) trying to get ahead of you. Lastly they may be the only company in Silicon Valley to be low enough to give out (worthless) stock options that are almost guaranteed to be under water if and when they ever go public. All you need to do is look at other public (or bankrupt) fuel cell companies to get several data points for reference. Possibly the next Solyndra if you are willing to take the risk with your career.