I have been working with propeller as an advertiser for about 5 years. I can say that throughout the entire period the guys keep up with market trends and remain at the top of which other networks look up to.
The most important thing is that in my opinion they are valued for the fact that they do great job and have very large, I would say exclusive public pages with high quality traffic.
I would also note the presence of CPA targeting logic, which greatly simplifies life!
Account manager assistance with optimization of companies.
+ the ability to scale, the presence of a large amount of traffic.