As far as I know the only differences are the ones you point out. The code is the same.
OEM code is for system builders who have built their own machine, be it an individual or a company.
One rule with an OEM version is that once it has been installed on a PC it can NEVER (legally) be moved to another PC. The retail version can be moved if it is uninstalled from the original PC.
See here
http://blogs.zdnet.com/Bott/?p=166
Found this on the MS website
What is the difference between OEM product and Full-Packaged Product (FPP)?
OEM products are intended to be preinstalled on hardware before the end user purchases the product. They are �shrink wrapped� and do not come in a box like the retail products do.
Full-Packaged Product (FPP) is boxed with CD(s), manuals, and the EULA and is sold in retail stores in individual boxes.
The End User License Agreements (commonly referred to as �EULAs�) for OEM and FPP products are slightly different. One main difference is that an OEM operating system license (such as the license for Windows) cannot be transferred from its original PC to another PC.
However, the FPP [retail] version of Windows may be transferred to another PC as long as the EULA, manual and media (such as the backup CD) accompany the transfer to the other PC.