I use Sidebery primarily to manage tabs, of which I typically have many open. It seems to do a mediocre job of this. Here are the functions I use and my experience with them:

1. Move tabs within a window. For some reason, Sidebery's drag and drop is terrible. Usually, when I drop the tab on its new position, nothing happens. It typically takes 4 or 5 tries before anything happens. It's definitely easier to use Firefox's tabs than Sidebery's.

2. Tab Organization. Sidebery does support tree structure on the tabs, which allows for some organization. However, it feels awkward to use because of the drag and drop problem. Also, there's no way, as far as I can tell, to mark or label a tab or group of tabs, to make it easy to find later. Overall, a weak implementation.

3. Move tab from one window to another. Again, Sidebery has a problem. After a length of time, Sidebery "forgets" the titles of my windows, and shows only a generic list. To get the titles back, I need to shut down Sidebery and restart it. Unfortunately, this is pretty much every time I need to move tabs, which is fairly often.

4. Search for a tab. I haven't been able to find a way to do this with Sidebery, so I just use the Firefox feature of entering % in the search bar of a new tab.

Many users have given Sidebery 5 stars, despite it being a very mediocre
extension.

PLEASE do not rate this extension highly for no reason!

I wish people wouldn't hand out stars for nothing. It pollutes the Firefox extension ecosystem with misinformation, making it hard to shop for good extensions. This extension is not worthy of 5 stars, or even 3 in my opinion.

Because it still seems to be under development, I gave Sidebery 2 stars, which I think is fair and in fact charitable. If it hasn't improved in the near future, I'll lower this to 1 star, which I think we should all do.