Did it find alien life forms? No (at least, not yet). Did it raise the mindshare of Grid computing? Absolutely.
Even with the news that the project is being folded up into BOINC ("Berkeley Open Infrastructure for Network Computing") -- SETI@Home project has been an absolute PR machine for Grid computing for the last ten years or so.
Some in the Grid community would argue that while SETI ushered Grid lexicon into the mainstream -- it also relegated the mainstream understanding of Grid to a very narrow "CPU scavenging" type of definition. While so-called "compute-Grids" are in fact still the most prevalent types of Grids to date, the Grid community sees CPU scavenging to be just a subcomponent of the overall value proposition for Grids (which encompasses much broader capabilities in data virtualization, service-oriented infrastructures, and coordinated resource sharing between 'virtual organizations').
E.T. phone home jokes aside, SETI really appealed to the imagination of the IT community, and officially put Grid on the map.