Pros
Epic does its best to be a good company, and in many ways, it succeeds. Epic pays their employees well (in my experience, significantly better than average). They attempt to create the most productive working environment possible (they attempt to give each employee their own office, and the main campus is designed to provide places where employees can get out, but still be productive). They define a positive culture and (at least superficially) engage employees in the goings-on of the company. Training is not lacking. The travel requirements aren't overbearing (for software developers), and can be a lot of fun.
Cons
The biggest downside is the technology; VB6 was rightfully killed off by Microsoft 5 years ago, and MUMPS is a painful language to read. The architecture of the system hasn't significantly evolved from its original state, performance is lacking (the system slowed to a crawl in the middle of a class of 50 users), and the worst part is, the second-in-command considers the system to be "good enough" (which is never true, but that's unrelated). While the pay is good, career advancement is practically non-existent, and they explicitly state "if you have a goal in mind, you probably don't belong here". The best one might hope for is "promotion" to Team Lead, which happens generally to those that regularly put in 50+ hours, and generally just means more work for the same pay.