Pros
Depending on your job role, there can be great opportunity to make an impact. There are SOME visionary people who can make a positive difference for everyone they encounter. Decent benefits, decent salary, good continuing education (tuition assistance, professional development), standard package on everything else.
Cons
Everything is a sales-oriented numbers game to feed shareholders, at the expense of all else. Doing the "right" thing is wrong if it doesn't make a solid profit. Proven and accepted expert methods are largely ignored if something costs a few precious dollars. Certain members of management (not all) are woefully substandard, but are protected by a management "code of silence". Be careful what you criticize out loud, whether it is constructive or not; it could bruise the wrong ego. Watch: as personnel changes, so does the corporate culture, so be prepared to bend with it. This is not so much one big company, as much as it is a collective of smaller, regional offices (many of which were acquisitions), each operating with a great deal of independence - this kills any real ability to leverage experts from different offices.