Buy the retail version. Even if you do never plan on transferring to another PC, the OEM license can still be a pain in the rear if you ever upgrade the processor or motherboard. IMHO, the OEM version is just not worth the savings it the long run.
Microsoft support, bah that part of it really means nothing. How many times have you ever called Microsoft support?
I have the OEM version of Win 7 64-bit. Everything worked fine, including 1 instance of re-install.
Then I decided to upgrade my motherboard under EVGA's 'Step-up' program. After changing the motherboard and re-installing Win 7, I could not activate Win 7 online. Instead, I had to place a telephone call to Microsoft and then they activated my OS.
A PITA, but not terribly bad!