Avantages
Good pay - comparable to market. Let's face it; if you're working for an insurance company you're making decent money and not breaking your back. There are good managers. And many managers take interest in the employees. At least in my office, layoffs in other departments do weigh on the the employees and the managers. Many paths to success. Sometimes paths are cut short (e.g. those at the wrong place during a reorg) but employees in general are encouraged to grow and try new things.
Inconvénients
Large company means there are negatives here and there. Some managers may be incompetent. Some offices may have low morale. Some may be under-staffed. There may be a youth-bias in hiring, but it's not ubiquitous. But frankly, the naysayers can only speak for themselves. Obviously, they will not know the whole organization.