The Q2 2011 Service Release of SQL Azure introduced the updated spatial data platform from SQL Server 2012. SQL Server 2012 spatial features are being released in SQL Azure in increments, beginning with Q2 2011 Service Release. With the introduction of the Q4 2011 Service Release for SQL Azure, a new TechNet Wiki post, Updated Spatial Features in SQL Azure Q4 2011 Service Release, is now available, providing the definative guide to the new SQL Server 2012 spatial features making their appearance in SQL Azure.
The Q4 2011 Service Relase enables the following spatial features relative to the Q2 2011 Service Release:
Spatial aggregates (CollectionAggregate(),ConvexHullAggregate(), UnionAggregate()), and geometry::EnvelopeAggregate() now work correctly. Geography::EnvelopeAggregate does not work because it returns a circular subtype which is not yet supported in SQL Azure (see the post for more details). Additionally, the system view, sys.spatial_reference_systems, previously missing from SQL Azure, is now available.
For more information on the new SQL Server 2012 spatial features, please see the TechNet Wiki: New Spatial Features in SQL Server Code-Named "Denali" Community Technology Preview 3.