Editing my review, around 6 years later, after an ABSOLUTELY DISASTROUS update (v8.2 it seems) that got automatically applied today (this is why auto-updates are bad and I used to disable them all the time - I should have kept this up).
I use multiple separate profiles, each with distinct proxy settings. The update lost the extension settings fully in half of my profiles. In one of them (my main one, mind you), it SILENTLY DISABLED the SOCKS proxy that I had configured via Firefox's settings.
Luckily, I checked my IP that same day for another reason so I was able to detect that without my IP getting leaked for days or weeks or more without me noticing. But this could have been much worse. Totally unacceptable.

---- Old review below:

I used that add-on a bit pre-Fx 57, and it felt quite bloated at the time.

I tried it again after the WebExtension mayhem, and I really like this new version. For my rather simple use case (being able to use and switch between a bunch of SOCKS5 proxies that require username+password), it's quite perfect. I also like that it's easy to import/export settings, so that I can duplicate my config between my several profiles.

As someone else said, it would be nice to be able to disable logging, and apparently that feature is coming soon :)