On first glance, it looks like it could be very useful: it's very nice
to be able to do a search using a very generic term (e.g. "roi") and
get UX specific results from a wide range of sites. The downside, of
course, is that unexpected sources are excluded from the results (I've
configured it to show results only from specified sites because I
wasn't happy with the broader results set).
Please have a play with it, and volunteer to contribute to the site
list if you feel like joining in the fun.