Pros
This place rocks. They truly care about their product and their people, and that reflects in the kind of people they look for when they're hiring. They want someone who not only can identify a problem, but can enthusiastically come up with a solution. They really do want to be accommodating to work life balance, and expect hard work, but it's the best and most rewarding work you'll do around people who genuinely will celebrate and be happy for your successes
Cons
It's a start up, so there are kinks that come with that and rapid changes as the company learns and grows; however, it's not something that necessarily comes to the detriment of the employees. As long as you can roll with the punches and be understanding that literally EVERYONE has either gone through, or is going through the same thing(s) as you, you'll be fine. You're seriously well taken care of.