This addon doesn't work properly - the tabs opened after restart are (very) different.
Also - and this is really bad - here is the list of permissions used. How can this be justified.

Access your data for all websites
Exchange messages with programs other than Firefox
Display notifications to you
Access browser tabs
Access browser activity during navigation

I don't know who Nacho Vázquez is, but judging by that list I don't trust him.
I'm about to uninstall, but I will repeat the tip given by mjjordan :
If you want a TRUE Firefox restart IN TWO CLICKS, do this:
1) Type about:restartrequired in your browser
2) Drag and drop that page to your toolbar
3) Click "Restart"