I like that it was easy to use, they have some great tools for creatives that are simple enough so you don't need a high level of design skill or experience.
The interface wasn't super intuitive in my opinion but maybe this has changed recently? We weren’t able to see how many impressions we were getting from our ads until after the first day of running them - which led to us wasting time on non converting campaigns where we had no idea if they even worked at all! This also meant we could only view conversions when someone actually clicked through our link rather than waiting for organic traffic to convert organically over time (which isn't always reliable anyway).