I just watched such a cool video on YouTube, posted by an Orlando tile contractor. The video shows someone steam cleaning a grungy restaurant floor with a steam cleaner. It works incredibly fast, and increcibly well. If you are facing a major tile and grout cleaning challenge, consider renting a steam cleaner. One caveat with steam cleaning is that steam cleaners produce moisture. Be sure to thoroughly dry the area that you've cleaned, and ventilate the area, so that the moisture from the process does not promote more mold growth.