Some notes about upgrade process,

I don't want to waste the surprise to you, there is nothig so bad here, but if you like the suspance and to live it in first person you should skip this message...
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At the end of installation there is a message that announces a reboot is required, then the screen fills up of pseudo-random black spots until it becomes blank. Then nothing seems to happen. I had to press power button to make the tablet restart, then it booted and all was ok