Pros
Flexible hours. Decent cost-of-living versus other cities with software companies (if you're willing to relocate to Redlands). Good place for work/home balance, great benefits. Very relaxed atmosphere for the industry.
Cons
Very little connection with what you do and how the company performs -- financials are heavily edited and not readily shared, it's hard to get a grasp on what products are selling and your overall contribution to the organization. For a "flat" company there is a lot of structure and knowledge hiding; you need to know who to go to in this huge, role-less environment to get the information you need to do your job. On that, you need to participate in a lot of 'extracirriculars' like an Esri bowling/softball team or fantasy sports league to get an in on a cross-section of the organization so you know who to go to. Inter-team competition and occasional suspicion. For a software company, tremendously conservative about the use of new technologies. Like in many large organizations, you'll find yourself "busy" all the time, but not "productive." Many people love holding meetings for meetings' sake and are not taken to task for it. Being constantly exhausted with a full calendar and having nothing to show for it on a Friday afternoon is demoralizing. Flat is a euphemism for no promotions, difficult-to-acquire continuing education budgets, and COLA pay increases are all the raise you can hope to get most years. This company is the first I have ever worked at that is not hire-fire (no layoffs EVER!) which is great for job security, but the place has acquired quite a bit of dead weight over the years -- you can find yourself starting to coast if you're not vigilant.