I've been an absolute and unashamed fan of Google since the time I got introduced to it in 1999/2000 by a dear ex-colleague, Moinak (kewl guy, now works for Sun MicroSystems India) !
Their purchase and introduction of various other products has only endeared them more to me since then. One of their recent launches, Google Desktop Search (GDS) is quite impressive.
However, its inability to index and search PDF recently hampered my studies to such an effect that I *had* to try out Yahoo's Desktop Search. And, I must say, I'm pretty impressed with it too. This application gives a lot of control to the user and since it's a separate application by itself (not "embedded" within the browser), it gives a lot of options in manipulating, filtering, sorting searches and output results.
FWIW, I have written about other "add ons" to GDS (which include ability to search PDF files), however add-ons aren't the same thing as inbuilt stuff. The extremely kewl extensions for Firefox are not included in this discussion about add-ons :)