In order to ensure we grab the most widely used set of results each day we pull data from un-personalized, completely signed out version of Google.
If you are seeing rankings that look different than what you expect, make sure you are using a browser plugin to view what the average web user sees when they search that keyword.
Here's my two favorite plugins for spot checking rankings:
Local Maps Rankings
We calculate local maps results into our rankings, which may also cause our results to differ from other rank trackers.
In addition to the letter position, we will also continue to track the overall position on the page, so you always know where on the page your site is showing up.
Here's a good example that illustrates how we show rankings that include local maps results.
The keyword is 'portland plumber':