Pros
Overall a positive experience. Guidewire has a friendly culture, and management is dedicated in helping staff grow. Pay and benefits are not bad, and I find the projects interesting. Insurance won't cure cancer, but at some stage it may very well cover for the treatment that does. Having the chance to deliver software to help insurers reduce operating costs and improve user experience, all while working with and learning from very talented people, is, on its own terms, a satisfying and enriching experience. There's a big focus on work-life balance, as well as promoting a healthy lifestyle. Guidewire won't pay for massages, but they will offer you health insurance and make a physio available for you at the office.
Cons
I think Guidewire grew too much too fast, and, like most tech companies these days, is struggling to find all the talent it needs. Here and there you will find the occasional manager who is not as good as he should be, and you can expect having to teach design patterns to some of the junior staff. On the upside, some poor management means there's opportunity for climbing that ladder, and teaching junior devs can be a gratifying experience as well. As far as cons go, these are actually pretty decent ones to have.