Pros
Some of the best and brightest folks (across the board) I've ever worked with; for the most part, everyone is working their tail off to make the company successful. Slackers and others not up to snuff are generally filtered out quickly; there is no room for people to float along and hide their low productivity or ineptitude (in some cases, the cause of hurt feelings in other reviews here). Spending is conservative, in a good way. Money is not frivolously spent, although at times things are a little too tight, leading to some penny-wise, pound-foolish attempts to save money. The company culture is very much "as long as you get your work done, we're flexible". This certainly helps people maintain a reasonable work/life balance. Office environment is definitely casual, at least for people not working with outside entities on a regular basis.
Cons
The current open-office environment is noisy and distracting. Not enough conference rooms for impromptu (or scheduled) meetings. Office location at 101/Redwood Shores is a commuting nightmare. Luckily these issues are easily remedied once the current lease is up, and are not fundamental flaws in the company.