I like the theme and it is well done..but sadly it's unusable, at least for me.
What were Mozilla developers thinking when they decided to make the UI and menus so light they are nearly impossible to read? On this beautiful theme they are completely washed out against the vibrant background colors. It's too bad.
.

It's almost great! I love having a pride theme but the rainbow background is too bright and washes out the tab text. Makes it too hard to read. Could maybe just bold the font?