YES. Rated 5 out of 5 stars
Updating bookmarks to things like the last-read-page of a webcomic was getting REALLY annoying, so this is AWESOME.
One thing that could make it even better [note this suggestion is all assuming you have "Keep the old name" checked by default].:
It would be really nice to be able to control which entry is automatically at the top of the list in the shift-alt-d "replace bookmark" window, because that entry is essentially the default (ie, you get it by just hitting enter).
If I could set it to be automatically alphabetized, I could just throw an "a" or whatever in front of the names of the bookmarks I update a LOT, and update them in just two strokes without having to think about selecting anything.
(btw, I was curious, so I played around with it a bit and discovered that the order now seems to be produced by the same mysterious process that orders bookmarks when I ctrl-shift-b to open the "library" window. I have no idea how THAT's determined, because it sure doesn't seem to be by any of the sorting options you can manually select [name, location, date added, etc].)
P.S. Add me to the list of people who agree this addon should be a default firefox feature. =D
The sorting function compares the bookmarks by the length of the biggest prefix common with the current URL, and in case it's the same, leaves those bookmarks sorted as they are in the Places database. By the time of creation, I guess.
So, this is great for some websites (like Fanfiction.net, where the story identifier is in the URL, and comes before the chapter number), and useless for others, like Youtube (URLs have random identifiers).
So, doing alphabetic sorting by default does not fit this scheme, but I can be persuaded to add special sorting functions for specific domains. For Youtube, for example, it will compare page titles instead of URLs.