A thousand times this. Initially I wasn't a fan if I'm perfectly honest, but once I got my head around such brilliant things as the bang syntax I've been finding Google almost awkward to use by comparison. Being able to search Wikipedia with !w is brilliant.

This is built into most browsers--you don't need to forward the query through a third party.

For the curious, that's what the search "keyword" is for. Over time, Firefox has made it harder to add new search engines and find/modify their settings, but it definitely still works.