Pros
I've worked across multiple companies/industries in my 10-year career, and this is by far the most fulfilling company i've worked for. Employees are treated at smart, independent contributors who are encourage to solve problems with scalable solutions. My synthesis of complaints is most around not enough guidance and training. These are real concerns, particularly for people out of undergrad or unsure about their career direction. For people enjoy travel and technology, this place is just about heaven. The compensation is outstanding for how much fun I have at work. As a frequent user of Glassdoor, I'm usually wary of "fanboy" reviews like these, but this is honestly how I feel 1 year in.
Cons
Kayak is a fairly small company with a 500 person headcount. Unlike large global corporations, this potentially limits lateral move options and definitely limits geographic options.