Pros
Everyone really does demonstrate the core values of integrity, rationality, and collegiality. Those who don't will not last long. Not many "politics" being played here. Guidewire is well established to build and deliver a best in class product to a global industry that has traditionally been starved of innovation and which has a high barrier to entry. The company continues to exhibit strong growth; in revenue, profits, and personnel. Positions and roles exist today which did not exist even a year ago. The recession has not inhibited the company's growth. There is a flat hierarchy. Low emphasis on titles and a high emphasis on the value that you deliver.
Cons
The overall compensation package (salary, benefits, equity) is competitive, but you won't find luxurious perks such as a gourmet chef, tons of parties, a huge 401K match, daycare, or even free lunches. Conversely, you aren't expected to live at the office either. There is a flexible policy to maintain work / life balance.