I use this for almost as long as it's available on firefox, so I'm quite happy. The only thing I dislike it's that for some reason, when a segment is skipped, the youtube video do not always restart, loading in vain; if i manually move the playing time in the video, it plays normally without restarting the page. So I'm hoping this will be fixed because it didn't happen in the past (but since I do not often go on youtube, i'm not sure when it started to happen).