Based on the factory settings, I first installed Windows 8.1 driver all necessary support page of Lenovo. The result was a malfunctioning driver (Bluetooth Audio Device) and a more minute shutdown of the notebook. This behavior had not improved even after several restarts.
The installation only the necessary Windows 8.1 drivers (Intel Chipset and HD graphics) before upgrading to Windows 8.1 brought unfortunately no improvement.
I would still be able to live with the non-functioning "Bluetooth Audio Device", but the shutdown lasted too long and clearly very annoyed.
I am well aware that there are experienced users here who have successfully carried out such an update. However, I have no time and especially not like to have me shimmy under a really normal update process by all forums, so I finally 8.1 running on my notebook after several hours of trying a working Windows. The other manufacturers can better deliver the even partly my Windows 8.1.
For this reason, unfortunately, only two stars and a disgruntled users. I have returned the notebook to Amazon.
PS: For those who want to try it sometimes even a little tip. You can the Windows 8.1 update after installing two Windows 8 download updates in the store: "Although is the Windows 8.1 update from the store downloaded and installed, the PC requires the Windows Update KB 2871389 and KB 2917499 before Windows 8.1 represents in the Store. "