Not sure if many of you noticed, but post Windows Insider build 14936, the Steam overlay would refuse to work with 64 bit games. Starting with the public beta build of Steam that is available today, that issue is resolved.

You can opt in to Steam beta builds by going to Steam's settings>Account and clicking the "Change" button under the Beta Participation header. Select "Steam Beta Update" from the dropdown menu, hit OK and then hit the button to restart Steam.

As with any beta builds, you may experience bugs. I haven't run into any showstoppers in the time I've been running Steam betas, but your mileage may vary.