Pros
The company is very successful, and as a result can afford to compensate employees very well. In San Jose, the amenities are also very nice (on site gym, nice cafeteria, and a lot of social activities during and after work hours), and employees are encouraged to take advantage of them. The talent level of the software team is very high. Working with team members and other teams is an enjoyable experience.
Cons
Unlike many internet companies PayPal is driven by a precise business model (payments) as opposed to technology. This has led to the company's success in becoming the dominant online payment system. The downside to this is that much of the technical decisions and execution were done in haste in order to bring features to market quickly. Also, the nature of payments requires a high degree of coupling between the various components. Because of this the code and systems put in place sometimes makes it a difficult environment to work in.