I see big improvement on my RPC since widgetbucks started deploying the site category features, as of now the highest RPC I'm receiving is .33 and the lowest is .15 which is far better than .03 rate.
Widgetbucks is one of my highest online income generator aside from adsense. I'm currently earning at least 8$ per dayfrom one site alone.
I'm also thinking joining Project Wonderful as I read some good feedback from Macuha.com . 
I just received an email coming from widgetbucks saying that they are no longer charging merchants for international traffic. Visitor coming from outside of the U.S. and Canada will be redirected to non-paid pages, specifically www.mpire.com . Therefore no publisher credit will be given for those clicks, starting mid-November.
So what I did, instead of removing the widgetbucks ads on site, I download ip2nation database and installed it to filter the US & Canadian traffic for widgetbucks. Though I have a code that alternate both google and widgetbucks ads.
PHP function (modefied version of ip2nation script):
Then used if else condition:
