Rob Pegoraro at the Washington Post reviewed desktop search tools. He ends his article by saying:
These programs also shouldn't exist: Their capabilities should be built into the operating system, something both Microsoft and Apple are working on.
Exactly right. The opportunity for third-party desktop search apps exists because the Microsoft Windows file search is pitifully weak. As soon as Microsoft corrects this flaw, the opportunity will evaporate, as will the numerous also-ran desktop search apps.