Comparing the Update Scanner for FF57, as of 21Nov17, with its predecessor: I much prefer the old version. The new version opens sites in a page of its own, with a name like "moz-extension://f79626ca- etc. etc.". If you click on a link in the page it no longer works; on seeing a list of changed files, you can't click on any of them. This is a major issue for me.

It was convenient, with the sidebar opened, to click there to scan all pages. There may be ways round these issues, but they're not obvious. A nuisance, not major. I usually scan manually, setting the automatic scan to once weekly.

As many have commented, the scanner often reports pages to have been changed when there is no visible change; I expect that is unavoidable due to the nature of the pages, but is a nuisance.

On balance I still find the current version better than nothing; in particular I have a list of sites to remind me which to check. But it's got worse.