The first thing I want to show you is the new resource within Google WMT, namely the Structured Data Chart. Below you will see an image of some recent results from one of my sites. Not too much in there for structured data, and with a lot of errors.

Note a few things about the chart:

1. Note the location of the tool - Search Results / Structured Data
2. Note the number of errors remains fairly constant, then drops dramatically as errors are fixed
3. Note how frequently Google is crawling this site, even though it isn't ranking very well it is finding the error fixes almost as quick as I make the changes

Clicking on either of the rows in the table below the chart will open up a screen showing which exact pages Google has found structured data on, what types of errors (if any) are on those pages, and how many errors are on each page.