I find it to be 2nd best other then google. I use a few other PPC programs but CPX Interactive is paying the most. 3rd would come Bidvertiser.
what do you mean? Categorey, banners or popups? If so, banners and a few different categories seeing how I have it on 3 of my sites.
He probably mean TribalFusion, BurstMedia or Casale media which are extremely hard to get in if your site is less than half a year old or low Pr/Alexa rank.
I have been using them for a couple of months with pretty good results. I use a network called Direct Media Exchange that allows you to use several different CPM ad network together.