Pros
Huge amount of benefits working at SEL: health clinic, gym, 401K, Employee Stock Ownership Program. Work is very steady. Every Friday the entire company comes together to eat lunch, and presentations are given about what is happening in the company as a whole. Great work life balance.
Cons
This depends on the group that you work in, but the work that you actually do potentially could be very dry. I worked in software and developed xml drivers for relays, which was mostly tedious work. Also there's a lot of churn with different groups, so projects usually end up taking way longer than anticipated. SEL is a big company, so there's a lot of bureaucracy that you have to face when trying to advocate for a change in process or a new project. SEL loves process, and favors that over adopting modern technologies. If you're a software engineer that wants to work on software that uses some hot new framework or library, SEL most likely won't be a good fit. Their flagship software product called QuickSet is a 20 year old Delphi application. Almost every project I've worked on involves maintenance work. On the spectrum of "cool, hip startup" to "enterprise corporation" SEL is a lot more on the corporation side.