Well written and very similar to Multiproxy Switch Rated 4 out of 5 stars
This is a well written add-on and in many respects very similar to MultiProxy Switch which has now disappeared from the Mozilla lists but still available direct from the developers web site.
GuifiProxy lacks any facility to quickly open Settings without having to go through Tools / Add-ons . An option in the Tools menu would be much more convenient.
I do not think the toolbar icon is as clear as MultiProxy Switch when showing what proxy is set or if no proxy set.
Where GuifiProxy scores over MultiProxy Switch however is in its ability to import and export lists, but having said that you have to be very careful when importing a list as this will completely overwrite any proxies you have already manually established. This in my opinion is a serious flaw. I made this mistake and had to re-establish a range of proxies which I had not backed up. There should be an option to add to or overwrite completely any existing list. Cancelling at the import stage has no effect because the list has already been overwritten.
Also when adding a new proxy manually it would be more logical not to have to actually click on one of the proxies in settings and then click the add button before the pop-up screen appears.
It would be better to have a facility to automatically sort the list alphabetically like MultiProxy Switch without having to move each proxy up or down.
Addes quickly open settings with ctrl+alt+p
Added proxy to statusbar/addonbar when it is selected
Bug fixed add/edit proxy menu