The web stuff on Spolight is one of the first things I turn off on any new Mac. Siri is disabled, suggestions from the web are disabled, spotlight is only allowed to look at apps and files, etc. My mac works wonderfully after so that it returns results of what I expect when searched. Search is a lot less hard when you restrain it to searching only what you care about.
Spotlight, as in the underlying search technology and APIs originating from Mac OS X 10.4, is fantastic. Spotlight, as in the search box that appears when hitting Cmd+Space has become obnoxious and commonly thinks I want to know what 1 pascal is in inHg when I type "1pa" instead of thinking I want to open 1Password.
To this day Alfred remains one of the first things I install on a new Mac as a result. Still have access to Spotlight (the indexing service) search, but none of the extra "intelligence" (aka Spotlight the app thinking it knows better than me what I want) unless I explicitly ask for it by explicitly invoking an extra workflow for things like unit conversion, etc.
