should be none, you may get the occasional machine entry in EEM which will be from the failed activation, but no ill effects.
Please post questions in the community if you want general visibility.
In general, none. I think we were able to trigger a BSOD crash by taking a 513 install, synching it the first time, which caused download/upgrade to 517, and then pulling the battery. Other than that one (by a tester of course), we really haven't seen any problems.