Pros
Everyone I worked with at InterSystems was smart, supportive, and cared a lot about the quality of their work. I never encountered coworkers who weren't carrying their weight. People were always happy to share their knowledge and teach me things that I did not know. My manager was excellent, and my priorities were always collaboratively determined and clearly communicated. I was given trust and autonomy from day one, and I felt that I was always treated with respect. The company itself was very stable and, in my opinion, sensibly managed. As a privately held company, they could always plan for the next 5-10 years rather than the next earnings call. That translated to excellent job security and generally good morale. The work-life balance was truly excellent. I started each day between 9:00 and 10:00 and finished between 5:00 and 6:00. By 5:30 just about everyone had logged off, and there was never any expectation that I would be available after hours. PTO time was generous and it was expected that everyone use their full allotment every year.
Kontras
The culture at InterSystems was a little outdated. They were not flexible with remote work, and aggressively pushed to get people back into the office. (They had to walk back 3-days-a-week-in-office mandates multiple times as the various COVID strains peaked throughout 2021 and into 2022). There was also a business casual dress code that, while not an issue for me, was oddly anachronistic for a tech company. InterSystems makes a niche product with a lot of legacy code. It is highly performant, but the developer experience is not particularly modern, and it is very difficult to grasp the full scope of the product. That can make it tough to sell experience at InterSystems as applicable to other companies. It also means that the learning curve is enormous and there's lots of legacy code to maintain. Sometimes working there feels like being thrown in the deep end of 45 years of history without much guidance.