I like how easy it was to get set up, especially with their support team! They helped me through every step of getting my first Header Bidding setup running smoothly for our ad server - which we had never used before (and they didn't even know existed!).
The UI could be more intuitive in some areas but overall great product so far! We've been able have automated all campaigns' bid management from one place now instead having multiple spreadsheets/databases etc.- this has made things much easier than using other tools out there as well.