Although I couldn't live without Spotlight, there are occasions when it doesn't reach the areas that other search tools can.
EasyFind is one of those tools. It's a very powerful and highly flexible search app that should be able to find just about any file on your Mac. The good news is that unlike Spotlight, it doesn't require any indexing. You can just install it and off you go. The slight disadvantage of this, however, is that searches can take a bit longer because EasyFind trawls through your hard drive.
EasyFind could be useful in the case of hidden files or corrupted indices that Spotlight can't see. Some advantages of EasyFind over Spotlight include Boolean operators, wildcard search terms, searching of invisible files inside packages, and the ability to refine searches according to upper or lower case. You can also configure the file extensions you want EasyFind to search by selecting the preferences and a pop-out sidebar will allow you to define the extensions.
However, I found that the way EasyFind organizes search results - or should I say, doesn't organize the results - quite confusing. What you're presented with is a mass of folders and files relating to your search terms with hits highlighted in yellow. Although the depth of the search was impressive, crawling through the results to find what you need is much harder than with Spotlight.
EasyFind is a good tool to complement Spotlight for reaching those files that the latter can't, but I won't be switching to it exclusively until the results are better organized.