Pros
1) The salary and perks are already great and it will get a lot better in the future. 2) The technologies used for the projects are cutting-edge and you are give then opportunity to make a real impact at the company. While doing so you are also not micro-managed at all. 3) For a startup the work/life balance is awesome. Working hours are 9AM-6PM and working out-of-office hours or during the weekends is extremely rare. 4) The office is right next to the metro which helps a lot with your everyday commute. 5) The culture and people are awesome.
Cons
Not necessarily a con but oftentimes you are expected to step up, get out of your comfort zone and go the extra mile. This might make a few people feel a little more than uneasy in the short term but the returned benefits to your character and career development cannot be emphasized enough.