Pros
I never thought I'd look forward to coming to work every day. The biggest benefit working at Malwarebytes is the product itself. Prospective customers call in already raving about it, and they're right- it's the best malware detection and removal tool there is. This makes it easy to work here, since the culture is both very laid back and at the same time high-achieving. No one is micromanaging you as long as you're on top of things, and everyone is extremely cooperative. I've never received more thorough training when starting a new job, and therefore I was very comfortable starting my duties. The company is fun, and it's obvious that management cares about employee morale.
Kontras
Not a con, but a caveat. We are growing rapidly and it's likely that some of the "fun startup" feel will fade, and it will be harder to protect our culture and hire the right people. But I'm extremely hopeful. Usually you start a job and immediately learn about the trolls in the office and the boss' annoying habits. Not here.