Severe CPU load even with v1.0.7 - terribly buggy add-on, avoid! Rated 1 out of 5 stars
There are several unofficial add-ons with almost zero impact on performance, without the browser restart requirement while offering 100% the same functionality, for example:
It's a shame that the *official* add-on is such a terrible mess. There is absolutely no reason for this add-on to have such a severe impact on Firefox's performance. The "fixed" v1.0.7 still maxes out the CPU after a while and still causes enormous CPU load even in idle for no good reason at all (~10% right after startup on a modern i5-2400 vs ~0% in idle without the add-on, and permanently a maxed out core after an hour or two with the add-on). As far as I can tell, nothing has been fixed at all.
Additionally, there doesn't seem to be any other obvious way of contacting the dev(s) than through these negative reviews.
Dear devs, please follow this bug report and fix your extension:
Thank you for your feedback. We have submitted an experimental version 1.0.8 attempting to fix the issues that appeared in v1.0.7.
EDIT: We have just released v1.1.1 which reduces the CPU usage by this extension and improves the user experience.