raymii posted[1] over on gopher about some ways to override the new firefox styling. The post was so incredibly heloful to me (thank you raymii). Though it didn't quite get me exactly where I wanted to go.
I do not love change and I really dislike pointless change that only exists to justify someone's job (often the case for UI). The floating tabs really just donked my brain every time I opened the browser and felt it had to go.
If you read their post you will get instructions for how to enable a user stylesheet for the tab bar (and other locations). raymii's css was more opinionated about color and such than I wanted. Really I just wanted the tabs to no longer be weird floating things. If anyone else is look for this they can follow the instructions in raymii's post, but use just the following css:
.tab-background {
border-bottom-left-radius: 0 !important;
border-bottom-right-radius: 0 !important;
margin-bottom: 0px !important;
border-bottom-width: 0px !important;
}
#TabsToolbar {
border-bottom: 0px !important;
}
That will remove all space below the tabs and remove the rounding from the bottom corners (leaving the top rounded), but will otherwise keep all of your theme's styling in place. I tried to get it down to the minimally useful css and this seems to do the job well.