I'd recommend you steer clear of these guys until the dust settles. There is a class action lawsuit against them for taking people's money and not fulfilling their orders. Do a quick search online and you will see this is far from over.
I believe this depends on the build/release. I've done this with retail and technet builds and it always allows me to enter a key later. If I recall this was not the case with an HP OEM disc I used several months ago.
It's not a bad look but I just wished they'd fix then bring back offline viewing. I don't have a signal where I work and it would be nice to catch up on Linus Tech Tips when I have downtime.
You can define a software restriction policy using Microsoft's AppLocker. The benefit is that it's built into Windows 7 and beyond. http://technet.microsoft.com/en-us/library/hh831409.aspx