Pros
As usual, startups are in the beginning always chaotic, but that's part of the game. Make it or break it. Product itself has a huge potential to gain some momentum, and this anytime soon. Flexible working conditions, nice atmosphere, friendly colleagues, modern facilities. All that typical stuff what you can expect from any startup.
Cons
Maybe some things are not that well organised and needs attention or more clear structure. On the other hand, that's part of the startup world. Things can be accomplished either through strict processes or doing things cowboy style.