I started using Clickadu for running pop traffic about 2 weeks ago and I'm loving it so far. Clickadu has both adult and mainstream traffic and plenty of targeting/filtering options, including the ability to turn on/off proxy traffic. The volumes are good and the traffic seems quite responsive because I've had some campaigns take off there that were just average on other sources. I've also had two excellent AMs who got in touch from the start and have been helpful getting me up to speed, giving me some good zone whitelists and even creating some fully managed campaigns.
I've run a few campaigns with the 'Smart CPA' payment model, which is closer to real CPA than several other networks where 'Smart CPA' is only an 'optimization tool', so you're never truly paying "CPA" as such, just CPM that is optimized to try to look like CPA. On Clickadu the CPA pricing model is only available after you run a test first and if the campaign is successful enough then you'll be able to run a strict CPA campaign (and pay $X for each conversion).
I've tried one test push traffic campaign and I wasn't particularly impressed with the push option, particularly because you can only run one creative