Pros
Free food, happy hour, nice holiday party...um decent clients. Smart people (but it's not that unique of a quality) It's hard to think of things that were truly amazing. I guess that the people who last are really really hard working to the point that they'll give up their personal lives. They are upfront about this in the interview process so at least they have a tiny bit of self-awareness.
Cons
I know people have praised the tech but I found it to be buggy and never keeping up to performance standards in facebook's ads manager. The only amazing thing about the tech imo was the automation. Didn't care for how the management viewed the bottom line. I've never in my life worked for a company that was so anal about every dollar and cent in and out. You can be successful as a startup and not behave in that way. Attitude towards worklife balance. Again there will be long days in any company but no one should feel guilt ridden for wanting to leave the office at 6pm (more like 7..8..9pm and make sure your iphone is charged for late night calls). If i'm still working for someone and not myself, I'm leaving when I've completed my work. Face time is for the birds. There was a public shaming aspect to people not hitting performance metrics for clients. Putting them on the spot in large company meetings asking them to explain why daily spend was down a percent week over week. Really pathetic stuff.