Fundamental architecture isn't one of them
The GUI has changed, but I would wager (not having access to the source, nor development teams, of course..) that the scheduling, CPU and memory management, and drivers have not.
If there's a shutdown and/or reboot button (that's meant to be used more than a few times a year)... if you can't leave it on and it'll put itself in full standby within 5 minutes... if you can't bring the device back to life in less than 5 seconds... if you can't leave dormant applications running with no perceptible loss of battery life... then it's just a PC in a tablet case.
I really doubt that much has changed in one version. That's why there's RT.
