What's the catch here? This seems too good to be true. A lot of AAA titles for $5/month. I get that this is a promo price, but even $10/month seems too good to be true. I guess this is testing the waters for a Netflix style streaming service for gaming?
Having used it for a bit, there are some catches.
First, you have to have Windows 10, and have to update to the latest version. This went ok on my laptop but caused my desktop to bluescreen at every attempt. You also have to keep windows updated to continue using it, and Microsoft's updates haven't exactly been stable.
The second catch is this is basically a rework of the windows 10 store and all the downsides that entails. If you've never used the windows 10 store, it doesn't install things like a normal program, but rather as an "app" even though those are the same gooddamn thing. The "apps" run under a different process, and if you are like me and have different drives for different games, really restrict you in how and where you install them, trying to act much more like a mobile service. My guess is they really want windows 10 to be a "universal" os for computers, tablets, phones, etc.
The other hurdle I've run into is that a lot of the games, because they are the windows 10 app store versions, are really poorly optimized and ported.