Nice article, but I think that just as important as using checksums to verify downloaded files, maybe even more so, is using them to verify files copied between local storage devices, and between different computers in LANs.
I recommend that everyone should use programs that automatically verify checksums to copy files between devices (I.e. from local storage to an USB disk) or on a network. Most third party file copy and backup programs have this feature, but in many it's disabled by default and must be toggled on.
Hashing and comparing file / directory copying tasks to different devices or partitions should have become a standard feature on Windows and Linux with full GUI support, and enabled by default, a long time ago. The copy process will be about 15% ~ 35% slower but it gives peace of mind and can prevent serious headaches. Using this feature has saved me from future headaches a few times, when the copy program warned that checksums didn't match, due to corruption or because of antivirus meddling.
To automatically hash and compare files during copies, I use Teracopy; been using this program for almost 10 years, and in my machines I configure it to automatically replace the standard Windows file copy dialog. To just verify the checksum of a single file, or compare 2 existing files, Powershell works but if you want a GUI program there are many freeware programs that will do the job. My favorite is "CHK Hash Tool" - just open the program, drag the files into the window, and that's it (it automatically calculates the checksums). For more complex tasks, I'm sure most here have already heard of Winmerge - which not only compares files, but in case they aren't identical, it also can show how they are different.
When talking about backups, it's also very good practice to generate and keep a .csv / database with the checksums of all your backed up files. You know, in case the data in the backup media gets corrupt over time but not in a noticeable way (I.e. no errors during the backup restore process, etc). I've never done it myself out of laziness and lack of patience to deal with this, but it really is something I'd recommend doing.