Like many others, as soon as I had the opportunity to upgrade to Windows 8 I jumped at it, upgrading my Acer Aspire V3-571, which was happily running Windows 7. However, predictably, that's when my problems started.
Firstly, Windows 8 was unable to automatically find and install the Wi-Fi drivers for the Acer's wireless networking chipset. This was fixed by a quick Google search to find the Windows 8 drivers and manually install them (thankfully I was in reach of an Ethernet-equipped router!)
However, more painful to solve were the errors I encountered when attempting to update or install apps in the new Windows app store (called, creatively by Microsoft, the "Windows Store"). I tried a selection of remedies before fixing the issue.
Firstly, I changed from the local user account I was logging in with to a Windows Live account (you can do this by clicking on your user name on the Start screen and then selecting the option to change your account picture — intuitive I know). You need to log in with your Windows Live account if you want to use the Windows Store.
Secondly, I fixed my time settings. You can do this from the Desktop — either click the Desktop tile on the Start screen or press the Windows key and d at the same time). Click on the time in the bottom-right corner, select "Change date and time settings..." and make sure the date and time are correct — and to make sure, after any adjustments to your timezone, click on the "Internet Time" tab, click "Change settings" and then "Update now". Incorrect date and time settings are known to sometimes cause Windows Store errors when installing new apps.
Finally, the last thing I did to fix the issue was use the new Refresh option. On the Start screen open the Charm bar (by moving the cursor to the top-right corner) and search for Refresh (you will need to click "Settings" in the search results to see it). This will retain your user settings and files, but you will have to reinstall any apps you have installed through methods other than the Windows Store (so applications downloaded from a website, for example, or installed off a DVD). (You'll also need to re-log in to your wireless network afterwards.)
This fixed the issue. Once it had finished, the Start screen was exactly as I had set it up, all my linked accounts were still functional and I could happily install and upgrade apps in the Windows Store. Hallelujah. (I'm still a tad grumpy about Wi-Fi not working "out of the box", however.)