I really like that it's an easy platform for publishers, as well as advertisers/brands who are looking at ways of delivering ads in different formats (like video).
If there is anything i dislike about undertones its their UI - which could use some improvement! We're able to deliver multiple content types via this ad network including videos & rich media banners through one feed instead having two or more networks with separate feeds per format etc.. This also allows us better targeting than other competitors by allowing our clients access into both direct audience data but across all available channels they have campaigns running eCPMs up from $0-400+. It has allowed me time spend managing my account rather then thinking what kind banner will be delivered next week!! The customer service provided isn't always very helpful so please ensure your asking questions clearly before contacting them directly instead using twitter hashtags #undertonesupport would save many people hours if not days worth waiting.