Pros
Company growth and stability is good. The people are great - there are always a few bad apples, but this is the most supportive environment I've ever worked in. Work/life balance has been pretty good in all roles I've been in, but better in some places over others. Benefits are good; PTO at the onset is nice. Pay is both high and low - low compared to other financial and regulated jobs, but high compared to other places. Assorted perks, like having an on-site nurse, are very nice. They are slowly moving into being a more progressive company, in the last couple of years opening a downtown office, encouraging work from home and flexible working environments, casual dress, etc.
Cons
No advancement. It is a running joke across Discover HQ that you have to leave the company and come back to get promoted. HR and hiring managers are very quick to promise a lot of things regarding career path or promotions that never materialize. If you are willing to wait 5-10 years before being promoted, you'll love it here. If you are young and hungry, it's a good stop before heading elsewhere (which is sad to say, because the company is really great). As with most of corporate America, get used to re-orgs every six months. If you have the same role and same manager after a year, you're a rarity.