You can easily search and replace all bolded or italicized text in a document, for instance. Or you could remove that ugly Heading 2 style they used what were they thinking using bright red?
Open up the Find and Replace dialog from the menus, or just use the Ctrl+H keyboard shortcut.
Click in the blank Find box, and then you can use the regular keyboard shortcuts to specify specific formatting. For instance, if you wanted to replace all bolded text with regular text, you'd use Ctrl+B in the "Find what" box, or for italics you would use Ctrl+I. You can even use multiple search criteria here.
If you have styles that are more difficult to replace with simple keyboard shortcuts, you can click the "More" button on the lower left-hand side to show a lot more options.
The "Format" dropdown will give you access to select specific formatting options, like fonts or styles. Just make sure that you first click in the "Find what" box before you select an option.
For the "Replace with", you'll need to click in that box first, and then select the options that you want just the same