Vantaggi
Promising technology with frequent updates that are useful and often game-changing; intelligent employees in every department that are carefully hand-picked, awesome benefits; long work weeks sometimes, but understanding management that will let you recover when you express the need and/or you need to attend to your personal life
Svantaggi
If you don't love working in a startup environment or have never done it, then you need to know that you must go beyond a 40 hour work week quite often. Weekend work is necessary sometimes. BUT the potential to contribute to such a promising company's success makes it worth it. General advice that applies here: if you don't believe in an earlier stage company and can't give 100% and then some, then look somewhere else.