Your experience with various ad networks? Looking for testimonials

I'm just reviewing various ad networks and what they have in store.

Would basically need the following:

- possible to load the account with a test budget and spread over a number of traffic sources / campaigns for a smaller amount of $ to do some A B testing
- possible to select traffic by niche / site in the marketplace
- geo and language filtering
- ideally to be able to pick the site or even the spot / ad type where the traffic comes from
- optionally selecting keywords (not sure who offers this, know that AdXpansion offers keyword bidding)
- CPM preferred over bidding

As I understand that results depend on way too many factors, I'm not looking for any bashing or promotion of any of the companies, but for feedback from those that actually use these as a publisher or as an advertiser.

Registered accounts with:

- adXpansion
- EroAdvertising
- ExoClick
- JuicyAds
- TrafficForce
- TrafficHolder

and know some great professionals working with them.

Would like to hear some experience from those who actually use these, what you like, dislike, what works for you, what would you suggest to improve etc..

Thanks!