This is just another example of why Windows 7 is still the best OS there is. Apart from being already a 'walled garden' platform, this will make the user be in even less control. This new feature will take up memory and internet speed, and will wreak all sorts of havoc. This like that feature in Vista where the applications you frequently open are saved in the DRAM and therefore will load faster, but only ended up eating precious memory space and slowing the system down.
This feature is still in Windows 7 (and 8). The memory used for it is just reported differently in 7 and beyond. And it works great, unused RAM is wasted RAM!
You also missed that 8.1 "will allow" automatic updating of Metro apps. This is no different from allowing Windows Update to install patches for Office on Windows 7.