Exciting mission, impressive leaders and people, focus on innovation and doing something very important (better energy storage) for the world in a fairly new industry that still has a lot of room for technological improvement. Very good compensation and benefits. Flexible time of work and location for most. CEO has a great work ethic, excellent experience, and heart - he really cares about people not just the bottom line. He's among the most impressive CEOs I've ever worked with/for.
Cons
Not a lot of handholding or documented process yet - for some who like to help build that their way, that's actually a pro. Still early stage so depending on the group and team, the expectation may be to work more than a 40-hr week.