I never really used Sherlock before I installed 10.2 (except to find files, which it doesn't do anymore anyway). After I installed 10.2, I tried out Sherlock 3, and I do believe it kicks booty. I wowed my girlfriend last night by showing her trailers (full-length, not TV-length) for various movies we want to see...
But there are still many other "channels" I would love to see. Among them: white pages (wasn't that on the last Sherlock?); maps (more like Mapquest, instead of just tied in with the yellow pages); news tickers; MP3 searching; concerts/arts listings; local guides (like Zagat's or Citysearch) and others I can't think of now. This could really turn into THE killer app for integrating the web more fully into the computer.
Can third parties make plug-ins to accomplish these tasks? Or do we have to wait until Apple does it? It would be really cool if the plug-ins were easy enough to make that many websites could offer them (kind of like Avantgo for Palm users).