You can try out my Network. We are accepting publishers in our ongoing beta program. We have good rates for leaders/banners and pops. Just check out my sig.
I would say that ValueClick is now a 3rd tier network. They are paying me around $0.15 - $0.40 CPM, but the earnings seem to be getting lower all the time. I have never experienced these low earnings before when it was FastClick. Casale is paying much more money.
I use to get around $3 - $5 with just popups with ValueClick. I don't use popups now though as popups just make people want to click away from your site.
No, they have a 12 hour minimum popup cap, meaning that 1 popup will be displayed to one person every 12 hours or something similar to that. If their fill rate is crap then I would suggest that if you want to use popups then you should do what I had done by using defaults so that you can get more of a fill rate by using other networks to fill your ad space.