Pros
ServiceNow's product is powerful and will be useful to many clients for a long time. The company is on solid ground financially. Corporate culture is pretty good in general.
Cons
Pay is low for the area--even for today's climate. The architecture is...bizarre. Don't expect to build sites using relevant technologies like React, WebPack, etc. Building apps for ServiceNow means writing pre-ES5 JavaScript into CSDATA blocks in XML then hand-copying files to the right repos. There's never truly been a paradigm like this, but if I had to place it, I would say SN's engineering practices are somewhere in the early 2000s to early 2010s on average--light years behind the average. The impact of this is up to you, personally. I found it jarring. Also, this may be specific to my team, but despite having 2 days/week in office, I am completely isolated. I'm vaguely aware of neighboring teams but not who to contact to reach them. I've never had a skip-level meeting and didn't meet my boss's boss until over a year into my job. I've barely met anyone outside my team, despite the clear architectural opportunities to modernize and improve broad Engineering practices and technologies.