Updated, October 25, 2012: Updated for the final version of Windows 8 Upgrade Assistant.
General availability of Windows 8 has finally arrived. If you're considering upgrading your current PC to Windows 8, you might want to check your PC for compatibility first. Here's how, using the Windows 8 Upgrade Assistant:
To download the Windows 8 Upgrade Assistant, go to the Windows 8 upgrade site, then click on the blue Download Upgrade Assistant button. The file is only about 5MB, so it shouldn't take long for the download to complete.
To run the upgrade assistant, double-click on Windows8-UpgradeAssistant.exe. It will immediately begin checking your PC for compatible apps and devices. Once it's finished, the Upgrade Assistant will display how many of your apps and devices are compatible, and how many require your attention.
Click on the "See compatibility details" link for more detailed information. If you want to continue and upgrade to Windows 8, go back to the main screen and click Next. Otherwise, exit out of the upgrade assistant.
That's it. If you don't find your app or hardware listed in the Upgrade Assistant, you can also search the Compatibility Center for Windows 8 Website to see if it's been added recently.