I've looked at PlugRush several times but so far I haven't done more than sign up so I could have my very own spam link
http://www.plugrush.com/?ref=14994 
I haven't put them on any of my sites so far mostly because I don't really build sites where I want to provide space for plugs promoting and directing traffic to other sites. At least not unless I make a lot more than a few cents. It's the same reason I don't have Juicy Ads or other similar ad networks on my sites. (I should mention that I've used Juicy Ads as an advertiser but not as a publisher.) I only make space for prepaid advertising spots from individual advertisers who are willing to pay a fixed price for monthly or longer ad space.
The individual advertisers part is important to me. Because just like with using RON (run of network) when advertising, the thing I don't like about PlugRush is that it seems you have to create ad zones and let ads (plugs) start running with no advance control over what appears on your site. Then you can block ads/plugs from sites you don't like *after* you see them on your site.
At some point I may try building sites designed for this kind of business model. But it's not something I'm doing right now.
I do see that a lot of people use PlugRush, so for the right kind of sites I'm sure it's a good option.
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