MoPub was a mobile ad server owned by Twitter since the September 2013 acquisition, acquired by AppLovin, and now part of the MAX mediation platform. MAX gives users a diverse set of auctions for supply.
MoPub is perfect for US in app campaigns. They are able to offer inventory worldwide, but clearly the US is their home turf and the place where they feel most comfortable. They work well for performance campaigns, but I would not use them for branding purposes. They are very responsive and keep improving their product offering to stay competitive.
MoPub is a great SSP. It is a trusted partner that can help you scale campaigns as well as educate the client about the benefits of programmatic advertising. They have a lot of inventory and a great support team. I wouldn't say they are perfect because reporting is not very good and some billing issues are not as transparent as they should be.
MoPub's support is really good. Their team is knowledgeable on their product and the programmatic ecosystem in general and they are very helpful. The only 2 things that I would point out would be that their response times are not very fast and that there is a lot of rotation on the account management team.
We've been attempting to make AppLovin Max perform the same way as MoPub had for us. The value we get from AppLovin Max differs from the ROI we get from other mediation platforms. We keep convincing ourselves that AppLovin Max will eventually function similarly to MoPub.