It allows you to sign up (for free) and earn points towards getting your site stumbled while you do the same for other sites.
So far what I like about this is that unlike Traffic exchanges where you can't control the sites you view, this service allows you to pick and choose which sites you want to stumble. Therefore, helping to keep spammy sites out.
You can view the site first, decide if its something you consider "stumble worthy" and then make your choice from there.
It's free but you do get referral points for everyone who signs up.
This is NOT my referral link. But if you care to share the love, the referral link is in my signature.
I'll be curious to see how the traffic on this pans out.