Pros
Top quality people serving the best customers in the technology industry. Co-workers who are better than you at something and willing to make you better, too. Leading the industry and working closely with technology leaders. Opportunity: to grow, learn, shine, be recognized. An emphasis on the employee (the "Racker") that is so ingrained in the culture of the company it is part of the CORE Values of Rackspace -- this makes sense because the only way to have employees who care deeply about their customers is for leadership to care about their employees.
Cons
Compensation is not the leading draw for people to work at Rackspace. The culture, access to top technology, opportunity for professional development and the coolness of being a "Racker" means people are willing to give up top dollar for quality of work and life. If money is the prime motivator for you, you'll be disappointed.