Considering the amount of traffic my router blocks EVERY DAY by machines infested with viruses because they're missing security patches I could see this as having some very positive effects, though I agree with wondering how they're going to implement it, as for having the decision made for you, you gave that right away when you agreed to the EULA. I'm pretty sure that there is a clause that reserves the software as the IP of Microsoft and they reserve the right to make "necessary" changes as they see fit.
Also, if you're using an AMD processor you'd much rather be on SP2 anyway, much better support for the chips
I just disable the Security Center features and go about my merry way.