Pros
Some very great people to work with, inside of a good culture. At its core, Discover cares about the employees and even the communities in which they work. I volunteered 4 years in a row for building playgrounds in areas around Chicagoland. It fostered teamwork that you simply can't achieve in the office. At some point long ago, they renamed their IT department "Business Technology" claiming that their technology is so important to their business. I'm not sure that it goes much beyond claim anymore - it used to though. They can be very flexible about "working from home" and used to provide very good time off banks (I received up to 6 weeks / year, for example).
Cons
Moved to implement ITIL methodologies about 5 years ago, but did so via force rather than training personnel and explaining how/why it's useful to the company as a whole. Over time it's worked out, but it's ultimately what drove me to leave. Also, it can be difficult to continue to move up the ladder within IT (non-application development) as there's very little growth in that area. In BT, there are some strong personalities who don't like to be told "no", even when using constructive criticism.