This information came out in RC2 and we'll see if it is changed once ConfigMgr 2012 goes RTM.

Supported versions of SQL Server 2008 for RC2:

·        SQL Server 2008 SP2 Standard and Enterprise  CU7

·        SQL Server 2008 R2 SP1 and CU4

·        SQL Server Express 2008 R2 and CU4 (secondary sites)

http://technet.microsoft.com/en-us/library/gg682077.aspx#BKMK_SiteSysReqFunction

A note about SQL Server Memory Note:

When you use a database server that is co-located with the site server, dedicate 50 percent of the available addressable system memory for SQL Server.

When you use a dedicated SQL Server, dedicate 80 percent of  the available addressable system memory for SQL Server.

Configuration Manager requires SQL Server to reserve a minimum of 8 gigabytes (GB) of memory in the buffer pool used by an instance of SQL Server for the central administration site and primary site and a minimum of 4 gigabytes (GB) for the secondary site. This memory is reserved by using the Minimum server memory setting under Server Memory Options and is configured by using SQL Server Management Studio. For more information about how to set a fixed amount  of memory, see How to: Set a Fixed Amount of Memory (SQL Server Management Studio).

If the install is almost complete and then rolls back, try this fix and give the SCSM services a bit longer to start http://support.microsoft.com/kb/922918

Applying a CU for Service Manager and getting "Patcher returned error 1642:Unknown error (0x66a)"?  Odds are you are trying to apply the wrong CU.  For example, you downloaded CU3 for Service Manager 2010 and you really meant to download the CU3 for Service Manager 2010 SP1.  Make sure you are applying the right bits and it should take care of that particular error.