Such tools include Webferret, Copernic, Sherlock, and Intelliseek Bullseye. This allows deeper and more extensive searches to be performed in a reasonable amount of time. However, typically such services make it more difficult to analyze community usage patterns to improve relevance. Also, the download is something many users don't care for. And finally, of course, the download products cost money.
Profusion looks like it is on the way to being a very solid metasearch tool for advanced users.
It just goes to show that for tough research problems, there are no magic bullets, and advanced researchers may still need to know a bit about selecting the best search tool for the job as opposed to relying on a metasearch engine to do the work for them. Between Metacrawler and the popular Dogpile , acquired by Go2Net in August 1999, Infospace is the clear market leader in metasearch. In past reviews of these engines, I noted that Metacrawler's lead was largely justified by its powerful features and customization capability. Nothing has changed here. My feeling on Dogpile was not so kind.