Pros
Top reason to work at Box.net: awesome employees. The Box crew is a smart, passionate, slightly nerdy bunch - a good mix of motivated young employees and experienced executives from top tech companies in the Valley. Senior leadership is accessible, and all employees are very committed to making Box.net the top product in it's category. There are also lots of perks, like free daily lunches, including a Friday all-hands "family" lunch, and great benefits. The office is also cool - a three-story New Orleans manor-style building with lots of open spaces, including a big kitchen and rec room with a pool table.
Cons
The commute from the city (San Francisco) can be rather arduous, so a lot of employees live locally. Also, if you're not self-motivated, Box.net probably won't be a good fit as there's very little micro-managing - employees are given a lot of free reign and independence, but are expected to deliver!