Mag, sorry I didn't get back to you sooner. As far as I can see the downloads and activations are not a problem. You will need to deactivate copies before building a new system or reinstalling your OS I would assume. Though I just migrated from Window 7 RC to Windows 7 Professional and the game (Dragon Age) was on a separate partition and works fine from either copy last I checked.
You can even register your DVD keys and download a copy from EAs site if you break or lose the disc. Not bad as far as I'm concerned. Not that most of us will use the feature.