Blogcritics used Rollyo for a while a couple of years ago, and I was never happy with the search results or the way they were displayed. It could have been some setting that BC used, but I assumed it had more to do with the way Rollyo works.
When I was at Blogworld last fall, I chatted with the folks at the Lijit booth for a while and made a note to take a look at their product when I got home. Apparently so did Phillip Winn, the Blogcritics Chief Geek, because not long after, Lijit replaced Rollyo as the site’s search tool. It’s worked out well.
Rollyo’s web search is powered by Yahoo Search, so I can’t see why I would want to use it as a general search engine. I think that Rollyo’s best value is as a search engine that looks at a specific collection of websites. This might be handy in a library if you have, for example, a number of different digital collections being served up from different domains or subdomains. With a Rollyo (or similar) service, you could build a single search interface for them. That is, if you don’t mind sending your users to a site that mixes in six paid links for each page of ten results, in addition to side-bar advertisements.