This extension doesn't work as expected:

I'd like to use it to archive my article listings on eBay. If I save such a page using SingleFile and then open the saved page, the image magnifier and most other interactive elements do not work. This problem appears in every browser I have tested (Firefox, Chrome, Edge, all up to date at the time of writing). I already have unblocked every resource type in the "Network - blocked resources" section of the extension's options.

Further investigation (looking at the console in Firefox) showed that Firefox wanted to load a bunch of scripts and other resources from the eBay website when opening the saved page. This failed due to the Content-Security-Policy, which is understandable. This means that SingleFile does not download scripts and other resources as expected, or does not save them locally, or does not change the URLs of such resources in the saved page so that the resources' local versions are used when opening the saved file.

Given that, the extension is not usable for me. At least, it doesn't provide anything that "File -> Save Page As ..." does not provide as well (I don't care whether or not a saved page is contained in a single file, and every browser except Firefox can save a page to a single file anyway).