In case you are not aware, there have been some significant licensing changes in the SQL 2008 R2 release, especially with the introduction of the DataCenter edition as the top-of-line edition. SQL Books Online documents the facts, as always, but sometimes it’s convenient to just understand what are the deltas. Towards this, I was made aware of the following article from Directions on Microsoft:

This article contains a nice tabular summary of the facts. I found it useful, and I hope you do as well!

Many thanks to the folks at Directions on Microsoft.