Pros
Really fantastic local team spirit, collaberation, work life balance. At times the employee perks were referred to as the golden handcuffs as they were so good (reduced working week, working from home, flexible hours) that nobody ever wanted to leave. This was a couple of years ago now, so is a little outdated. Opportunities for career progression were good and some of the most organised product owners and BAs I've had the pleasure of working with.
Cons
The application is a huge monolith and you will likely spend the vast majority of time adding to a well established framework, writing business logic in the back end and UIs. This does not really represent the expectations of modern software developers, where being a good developer involves everything from build pipelines, new libraries and packages, ORMs, cloud native, APIM and generally how web apps and apis actually hang together. The flagship product is also stuck on legacy versions of .NET and a Javascript framework that is not used by many others, which means as a developer you are really limited in what you can learn on the job to progress your own ability and remain employable.