Pros
Castlight is on the path to meaningfully improving the healthcare system in the US - helping Americans get better care and a better price. Employees feel the passion of being on this important mission. At Castlight you are surrounded with super smart highly motivated colleagues. At Castlight you have the opportunity to learn a lot, watching a company grow, led by experienced leaders.
Cons
Some people might say "enterprise" isn't as hot as consumer, but I would argue it creates a platform for dependable and stable growth. Some people might shy away from health care as an industry, but the reality is that its an incredible industry, and will be a place of incredible opportunity for the next 20 years as the US system undergoes a substantial transformation.