Surprised they're pulling the plug on this. I didn't particularly find it useful as an end user but it was a developer tool for the most part. I occasionally sideloaded some games to fool around with but I could never get most of the features to work for proprietary food apps, like GPS and such. It would have been really nice to be able to order McDonalds and whatever from my computer instead of needing to do it from the phone.
Hopefully the subsystem will still function more or less and we can keep sideloading even after deprecation.