Microsoft has begun the process of rolling out hundreds of millions of free Windows 10 upgrades. The Get Windows 10 app, which is being delivered as a Recommended (automatic) update to Windows 8.1 and an Optional update for Windows 7, does a compatibility check and should notify you if you have any devices, apps, or compatibility issues that will prevent a successful upgrade.
But just because you've registered for the upgrade doesn't mean you're completely free of potential problems. In my experiments with the Get Windows 10 app, I've discovered that it didn't notify me after it found some apparently minor issues with a couple of upgrades.
If you want to check your own Windows 10 upgrade report, follow these steps. (Note that you must have installed KB3035583 for the Get Windows 10 app and its associated icon to be available. You'll find it in Windows Update, as a Recommended update for Windows 8.1 and an Optional update for Windows 7.)
Step 1: Right-click the Get Windows 10 icon (on the right side of the taskbar) and then click "Check your upgrade status."
Step 2: In the Get Windows 10 app, click the hamburger menu, which looks like a stack of three lines (labeled 1 in the screenshot below) and then click "Check your PC" (2).
Step 3: See the list of potential compatibility issues. The list includes separate categories for devices and apps.
So far, most of what I have seen has been minor. If you see more significant issues, I'm interested in hearing about them. Leave a comment in the Talkback section below or, better yet, send me an email using the contact form in my bio. Be sure to leave a correct reply address so I can follow up if necessary.