Pros
Coming from a long stints in smaller companies, 1E was a bit of a shock to the system in many ways, but not in a bad way. I've been in 1E 7.5 years or so and have had an exciting time here in many ways. At first it was settling in and working with 60+ other software development team members in an Agile environment that was new to me, but thankfully my technical background allowed me to excel in many aspects that compensated for my own perception of my weaknesses. Coming up to speed was quick. I've since worked on about six major products in my time here, from mobile apps through desktops, servers, Windows, Mac, various Linuxes, Solaris through to Azure Cloud. We are shuffled around as teams form and disband, be prepared to see different aspects of the office, literally, as we also move desks about once a year too to group the new teams together. I personally have worked on some projects that were canned, this is the nature of the software industry and not unique to 1E. Although this is the longest job I've had in my career (I've a few 5 year stints), looking back sometimes I'm surprised how long ago events actually are, they really don't seem to be so many years ago in many ways, but in others they feel like decades ago, the pace here is quite fast. The diverse cultural make up of the whole company; the parties and fun; the hard work; the opportunities; they all make 1E a brilliant place to work.
Cons
1E is just as good or as bad as any other company out there, it depends on your previous experience and your career is what you make it. For me working at 1E has been occasionally frustrating sometimes but I think I would have the same experiences elsewhere, just different. Really you have to concentrate on your own experiences and drive where you want to go, who knows really why others might leave or stay.