Sorry to revive an old thread; it’s still relevant, though.
This isn’t true. There are standard tricks for all of these problems that would make it work just fine on even pentium-class hardware.
Also, seeing your messages in another thread, it should be noted that “adding an index” doesn’t mean rigid categorization, it means building (without human intervention) an inverted-index and maintaining it every time the OS notifies you of files changes. “Full-text” search doesn’t mean duplicating the full text of all your documents; it means building a mapping that lets you quickly dispatch short queries as they’re entered.
(Note–you don’t poll the filesystem constantly for changes; you let the OS tell you about them. That way, there should be 0 added idle load.)
You, @Dor might yourself know all of this already, but I thought the thread in general was lacking it.