Pros
If you have the opportunity to work with the Walmart.com team, you'll learn what's involved in running a multi-billion dollar website. There are a lot of moving pieces, and learning about the function of each one in the development, release and customer lifecycle is very rewarding. Some of the more interesting teams to work with come from outside acquisitions. These teams are not mired in the bureaucracy created by the way things used to be done. Also, there are lot of opportunities for data science within the @Labs teams. If you have a strong manager you will do ok in the "alignment" process for raises - if your manager is weak you will get screwed.
Cons
Where to begin... There is a huge lack of accountability for the success of projects at all levels. Years of work can be thrown out because of poor planning and coordination between teams. The current breakdown of WebOperations, Services and Markets is failing miserably... Poor leadership and no clear vision has lead to teams working on products with no clear customers in mind. The success rate for any of the new "pangaea" projects is non-existent. It's definitely not a meritocracy society within Engineering... Your relationship with the executive team will determine how high you move up within the organization. Web Operations is a total mess... The failure of the business rests a great deal on their shoulders, with services following quickly behind. Contractors continue to fill empty seats - the employee to contractor ratio is incredible. If you work on any of the customer properties (Walmart.com, Sams.com)- write off your holidays - engineering is on call 100% and typically onsite. At some point Bentonville is going to look at what they are getting for their money and there will be a major reorganization...