Pros
Fun environment, fast-growing space, potential to disrupt a large market and therefore, potential large business opportunity. Solid board of advisors. If you live in the area or nearby, it is great. For folks in SF or SJ, commute might not be great.
Cons
Box wants to be another Salesforce.com. It has a very expensive and not too-scalable direct sales model, which sooner or later will weigh them down as a public company.They have hired an unusually large number of VP and above-level individuals, which is also expensive. Too many VP-cooks in the kitchen and politicking slowing down decision-making. Some old-timers (in alliances, sales, product and engineering) stay there because of personal ties, despite their performance and/or behavior being dismal. Some really good folks resigned or were given no other choice but to leave. There have been under the table layoffs and plenty of turnover. Young founders. Diverging views between CEO and COO.