Without much fanfare on March 6, Microsoft announced System Center Advisor will be free for Microsoft customers in supporting countries (a list of countries is available here).
System Center Advisor, originally code-named "Atlanta," offers configuration-monitoring cloud services for Microsoft server products. The list of monitored products has grown from Microsoft SQL Server and Windows Server deployments to include SharePoint, Exchange, and most recently Lync.
Licensing for Advisor has always differed from the other System Center-named components. When first released in early 2012, it required you have Software Assurance on each server it checked. Microsoft's announcement last week has the product now offered at no additional cost to users of Microsoft server products.
Advisor consists of an Advisor web service, hosted in Microsoft's Windows Azure datacenters, and uses an agent (the System Center Operations Manager agent), installed on the monitored server. To read Microsoft's announcement, see this. For an evaluation of Atlanta is available here.