ok, but with strangness Rated 4 out of 5 stars
It works good and fast.
Some other users claimed it: sometimes, it does not open the tab/link on the other device (PC/Mac, FF25.0.1) automaticly, but most of the time, it does.
But what really is strange:
My iPad is listet about 12 times.
My Mac is shown 1 time and my PC is shown 1 time.
My iPhone is not shown at all.
And I see a lot of (null) entries in the List...
Strange, but I don't blame the developer, because I don't know if its a bug or maybe my broken sync-setup...
who knows, addon works great for simply just send a link/page/url to another device.
EDIT: some months later, I figured out, that old and unused installations or paired devices are responsible for the (null) entries in the list.
After reseting my personal sync password and creating a new recovery key for sync the entries are gone (most of all...)
You might have a look how it works here: http://superuser.com/questions/267413/how-can-i-remove-a-non-existent-lost-device-from-firefox-sync