That said, keyword searches are awesome and I use them for a whole lot of things, including effectively custom search engines. I have keyword searches against, e.g., internal confluence docs so I only have to enter "con <thing I'm searching for>" and firefox will load the confluence search page, or "people <name>" to bring up our internal phonebook with a search for the employee. I don't think I've ever needed to add my own entirely custom search engine to the browser.
