Windows Defender now has anti-virus built-in, so hopefully it will catch any nastiness before you install it. There's also the "improved" smartscreen filter, which still randomly decides to make me jump through ridiculous hoops to execute certain things just because they're not commonly downloaded.
It's especially fun since I run as a true limited user. Sometimes smartscreen demands "administrator approval" (not for elevation, it just requires me to enter my administrator password to run the application at all), and it uses a new type of metro-style screen overlay to ask for that, which doesn't support my fingerprint reader (everywhere else in Windows I can use it, including the UAC elevation dialog), so I have to enter my long and complicated admin password. This seems like a very curious oversight.