I have heard mixed reviews about it. Is it any good?
For Plugs BTW not popunders
There's not much volume and the lead quality is probably low, but you can make it work.
Volume is not really there, it's mostly plug (trading traffic) sites rather than big tubes.
Definitely better, but similar to Avatraffic, Trafficholder, Chokertraffic.
Thank you 
sorry I have to ask... what exactly are plugs?
On PlugRush, they are small banners with a snippet of text. They're usually embedded in the actual 'content area' of porn sites, drawing clicks from users who expect videos/pics rather than an advertisement.
I like PlugRush.
The OP mentions mixed reviews, which sounds about right. I've had mixed results.
err. no wait those were anal probes j/k
I like Plugrush, its very different though like stackman mentioned. Although there is little traffic, you can find very profitable snippets.
I suggest creating individual campaigns for each different source inside plugrush, blogs/tubes/babelogs etc so you can really find the profitable hot spots, its some of the best ROI you will find in adult.
Also make use of their dynamic tags, I'm talking really digging down deep. {$id} for the source ID {$domain} for the domain and {$cc} is for the country.
You can make money on any source, just become a master of it 