Pros
You get all of the perks you see in most startups, and then some. Instapage has snacks, catered lunch, and good healthcare. What really counts? The people. You will work with amazing people that are eager to learn, excited to grow, and are taking on big problems that need to be solved in this industry. Instapage is also in growing industry where you can truly make an impact. They give you the opportunity to really have ownership over your work and do big things. As a company situated across the globe, you have the opportunity to work with people from Poland, Romania and several other places where there are remote employees. This is a true startup and you can see the impact of your work in big ways within the product, in posts, and at conferences.
Kontras
You may work hard and you may do great things, but the likelihood you'll see those achievements rewarded in career growth are slim. Instapage might answer this with some statistics from how they've promoted people at the company, but it might be good to look at a team breakdown for this before relying too hard on this. That being said, you will have the opportunity to grow in ways that you cannot at larger companies - you just may have a hard time seeing this reflected in your title or pay. The loudest voices win. The loudest voices in the room are often the ideas that go to production. If you rely on the mantra "the best ideas win" you might have to find another strategy to get your ideas across while working at Instapage. This is a true startup. Things are messy and projects change fast. You have to be flexible and quick on your toes or you will be frustrated and fall behind. Things are not documented well because often there is not time to document in a way that people could reference. The work from home policy is a little frustrating and unclear. Vacation time is pretty flexible but it seems that within the SF office there is not a lot of trust from senior management that the employees were actually working from home.