What kind of Windows 7 does the "upgrade coupon" get you?

I was looking at the copies of Vista OEM on newegg that come w/ the "upgrade coupon" for a "free upgrade to Windows 7"

My question is not about Vista Business -> Windows 7 Pro etc... not about the versions.


Question:

When you use the "upgrade coupon" do they send you a full retail copy, a retail upgrade copy, or an OEM version corresponding to the Vista you're upgrading from (e.g. Ultimate x64)?

I ask this, because I will likely be building a whole new system March of next year and don't want to have an OEM copy that could be stubborn being installed on a diff system.

And I would also like the ability to install either 32 or 64 bit (which retail lets you,but OEM you have to choose one).

Thanks

So buying an OEM copy of Vista Ultimate x64 on newegg would get me a retail upgrade copy of Windows 7 Ultimate?

Has anyone had any experience w/ the newegg OEM copy w/ the "upgrade coupon"?

The reason I ask is, in my googling I've come across different opinions but no concrete answer from anyone who's actually done it. Some say it's a simple process. Others say MS makes you pick a manufacturer when you do it, and that building a PC yourself doesn't qualify (thus making the coupon worthless).

p.s. That link doesn't seem to work for me it just says " Error
In order to use this site, you must have Cookies Enabled on your browser." which i do have enabled.

thanks