What do you like best?
AppNexus offers tons of options for detail campaign management. There are many options for manual optimisations and reporting, giving you strong control over your activities. The system is very flexible and intended to be build upon or used in conjunction with other services and providers, either those who have app on AppNexus or completely external via integration, that multiplies the options I mentioned before even more.
What do you dislike?
The platform is quite complex and some features require relatively high understanding of underlying concept. This is difficult to grasp when you're new to RTB and DSP world. Certain principles seem to oppose each other in the first view which is usually due to lack of clarity on how these work together.
You are expected to read all the instructions in the wiki, but that is often not specific enough and in that instance you need to talk to support which is usually a painful, long chain of emails where you explain your questions. It would be better if you could talk to skilled technical manager at that point, but AppNexus doesn't provide such service.
Recommendations to others considering the product
AppNexus is great if you're fan of manual optimisations, however, as the industry grows fast, this might be obsolete approach soon, as person can't always optimise effectively on many points, whereas machine does. But until this is the main stream on the market and you are confident enough to tackle the platform, you can do a great job with AppNexus.
What business problems are you solving with the product? What benefits have you realized?
We usually run DR campaigns across the world. There is usually good coverage of all markets and lots of inventory, although in some geos (US in particular) we noticed high number of suspiciuos sites coming through.
As AppNexus is one of biggest consoles in industry and literally designed for integration with other system, it is usually one of the first which new data providers cover, hence you can test new data or other integrations among the first.