Wonderful! Rated 5 out of 5 stars
After years' searches and trials, there is finally a unified findbar/highlight solution! Nice work!
A few observations: once installed or related preferences are changed (e.g. change highlight color), if "Show highlights grid in the scrollbar" is checked, no highlight will be shown until Firefox is restarted. Also, after highlight color is changed, only the highlight grid color is updated. The color in the web page needs Firefox restart.
I did notice that the highlights color aren't updated until a restart if your firefox is set to apply the changes immediately on change, it is already fixed in the latest version 0.5.2, you can find it by clicking the "View all versions" at the bottom of the add-on page. Thanks for bringing that to my attention.
Now when you say the highlights don't show until firefox is restarted, that's serious, do you mean the highlights in general aren't shown or only the grid highlights aren't shown and everything else is fine? I can't reproduce any of these bugs, could you please tell me what operating system and firefox version you're using? And also would you mind trying to disable all other add-ons except for FindBar Tweak and see if it still does that, to rule out incompatibilities?