Pros
There are some really great people at this company, as well as they have a more than decent product. I did learn a lot especially about the HR business while I was there. Most people are willing to explain things to you. Please note I said most.
Cons
I left Namely at the beginning of 2017 and wanted to take a few months (about 5) to think about what I wanted to write as a review of this company as I spent about 18 months there. I had some really great experiences, but some also really bad ones. Most of my bad experiences were attributed to poor managers in the wrong role. Since I left I have heard that my manager was fired and the CFO was let go. Both didn't have a clear understanding of what needed to actually be done and how to get it done. They also had very little sense of priority. Everything was urgent. Nothing was thought through. I expect this from junior managers not from C level executives. There was clear favoritism on the team and when I approached my manager about it I was told I wasn't "likable enough" whatever that means. There were some voices of reason that tried to help me in other departments but nothing really stuck. I was asked when I put in my resignation if I ever thought about going to HR. The answer is no. Reason being is those who post on here that HR bullies for reviews and asks people to write them or sends you what you should write on here it's 100% true. During my first month at the company I was casually talking to one of the women from HR and she asked if I would leave a positive review about the company on glassdoor. I told her I didn't feel like I had enough experience at the company yet to leave a review. Pretty much every month she would ping me on slack asking me and once went so far to send me some text I could copy and paste into a review. So do what you want with that information.