Just wow!... I've been using another popular Youtube enhancer (Enhancer for Youtube), which just get so bloated. And now, I try this one and it does just what I need and much more.

The key/mouse binding is just incredible. Now I can map everything to work just as I configured my external video player (SMPlayer under Kubuntu).

Those are a few things that this addon does that the other addon doesn't (that I really like):
- Disable subtitles by default
- Frame-by-frame forward/rewind
- Much more control on fast forward/rewind (I use arrow for frame skip, ctrl-arrow for 3 sec skip, shift-arrow for 10 second skip and alt-arrow for 1 minute skip). Yes, I'm a shortcut-heavy user.
- Comments sorting customization
- And probably a lot more I'll find after playing with it for 5 minutes :-)