When on the main page of the Start screen you can start searching by typing like you could with the Start menu in previous editions. But instead of an itemized list of results showing automatically, it first shows results for Apps only.
Searching via the new Start screen.
And then you can select Settings or Files to show results on those categories. One good improvement, however, is that you can also select a metro-style app from the list to search that specific app for the word or phrase you typed.