Start here, learn as much as you can, leave, grow, come back, repeat ....
Pros
The Benefits, discounts on software, some really smart people to work with. The food in the cafeteria is sometimes good. What you are doing is going to affect millions of people.
Cons
The company is too huge ... slow moving ... sluggish. We need more ways of getting things done faster. It would help a lot if there was an easier way to reach employees within the company. We also need more visibility to product groups. It can be very daunting for someone who is starting afresh. Also, there is too much shuffling of upper management and product groups and not enough focus on long term strategy. The lack of openness is also a bad thing. Its about time more stuff was open sourced. It would lead to bugs being discovered earlier causing less of a problem.