This is a really useful add-on, it really helped me solve the problem I was having with youtube.
For some unknown reason, youtube's default "remember last position" broke, and every video played from the beginning, regardless of length.
With this add-on, the functionality was restored, and is now even better, since it accurately remembers the position every time, on all videos (YT's didnt work sometimes).
It would be even better if there was an option to not remember the position for the first few seconds (specified by the user), much like there is an option to not remember the last few seconds.
I think it would be easy to implement since there already is a similar function.