I'd be more worried about what is stored on the PC. Not to minimize the data being sent to Microsoft that they do who knows what with, but at least the chances of keystrokes linked to you personally getting in the hands of hackers through Microsoft are pretty small.
The stuff stored on your PC, on the other hand, would be just sitting there waiting for the first malware that sets up residence on your PC. If it happened to log your keystrokes when you are logging into your bank then the malware gets your bank password the moment it takes up residence in your PC. Even if tomorrow's AV update kills it off the damage is already done.