AWE (Addressing Windows Extension) is one of the know server configuration to everyone. This parameter allows SQL Server to access large amount of memory in 32 bit machines. However MS decided to depreciate this configuration in SQL Server 2012 (Denali) . I hope this is the first step towards depreciating all 32 bit SQL server editions. So if you are using this setting in your current environment then you need to be careful while upgrading it to SQL Server 2012.
Screenshot from SSMS where you can’t find the option for AWE
One more feature is discontinued in SQL Server 2012. It’s nothing but 32-bit Hot Add memory support is depreciated, so ensure you are not using this feature while upgrading to SQL Server 2012