I signed up back when there was a lot of interest and a huge backlog. I assumed they weren't going through so I kept submitting. Then about a week later I started getting flooded with emails with codes.
I'd do the PM thing, but I don't want to deal with it. First come, first served. Maybe post which ones you used...
I'm still sitting on two more codes. Remember that you need Win 8 Pro. So far my Win8 WMC has been working better than my Win7 it replaced. Doesn't seem to have the handshaking issue that would pop up randomly before.