Upgrading from Windows Sever 2003

Upgrading from Windows Server 2003 to 2008 got tricky, so I thought I should share some points to have in mind when upgrading

1) You cannot upgrade an x86 version (processor architecture) to an x64 version (processor architecture)
2) If you have an x86 version of Windows Server 2003, you'll only be able to upgrade it to an x86 version of Windows Server 2008
3) You can upgrade to an equivalent edition if the processor architecture is the same 
4) You can upgrade from Standard edition to Enterprise edition as long as the processor architecture is the same
5) You can upgrade to Datacenter edition only if the previous operating system is running Datacenter edition and the processor architecture is the same
6) You cannot upgrade Windows Server 2003 to any Server Core Installation option of Windows Server 2008 or Windows Server 2008 R2
7) You can upgrade from a Server Core installation option of Windows Server 2008 to a Server Core installation option of Windows Server 2008 R2 so long as the processor architecture is x64
8) To Upgrade from Windows server 2003 to Windows Server 2008 requires that at least Service Pack 1 is installed on the Windows Server 2003 host
9) For Itanium-Based System: Although Itanium is a 64-bit architecture, it's not the same as the x64 architecture. Hence, you cannot upgrade from or to an Itanium version of Windows Server 2008 R2 unless your existing version of Windows is the Itanium edition of Windows Server 2003 or Windows Server 2008