They often say that the longer the query, the higher chance of a conversion. So those who search for [widget] are less likely to convert than those searching for [big tall blue widget]. The intent is stronger and thus they are likely further along the buying cycle.
That being said, Google has designed a new dimension within Google Analytics to show data based on query word count. You can turn on the Query Word Count that can analyze query patterns easily, "without needing to classify them manually. Using this insight, consider adding additional long-tail keywords in AdWords to more closely match high-performing search queries," said Google.
Here is a picture of the report:
Now this is a cool and useful report to see at a higher level.
Forum discussion at Google+.
