Avantages
Nice amenities like free lunch, language lessons, company boat, social activities (karaoke!), etc. Budget and time for conferences and trainings. Room for intiatives, most colleagues are pleasant to work with, little politics. Try to stay up to date with latest developments, unfortunately doesn't go often into products (see negatives below). You can deep dive into the domain, it does not quickly get boring.
Inconvénients
Data-driven customer focus approaches like A/B testing are non-existent. New features do not come from investigating how people use the product. Tech and configuration debt is significant. Conceptual shortcomings inherent in the deepest levels, that were manageable before scaling, but now, not so much. Lots of time of the research engineers goes into maintenance. If you are applying for such role I recommend to ask exactly what you will work on during an interview, and let it be put in your contract. Lack of processes, roles and ownership. Also in the parent company. The deployment process is cumbersome and slow, they do not use the cloud. Because of all the above it may take years from idea to production. Some unprofessional leadership in R&D, criticism can be taken a bit too personally. There are a lot of people working there for 7+ years and/or fresh out of school, so there is lack of new ideas one could get from "outside".