What I think is quite archaic on the MS Store is if you have, For example, Gears of War, Forza etc... installed on a separate HDD and need to do a Windows format, Even though you have those games already downloaded and installed on your separate HDD, You have to redownload them all over again for your new Windows installation, That needs fixing ASAP, Steam, GOG, Origin, Uplay, BattleNet all have the ability to store games on a separate device and with a new installation of Windows or said programs you can simply point the application to the install folder, It scans it and if need be repairs any files and downloads missing portions.
This is 1 feature that should've been implemented upon the launch of the MS Store.