Pretty much every site uses the new topbar. Server Fault and SO are a bit different, but they still have the same topbar class as the other sites.

Right now, SOX is pretty broken on sites with the old topbar, e.g. Area 51 and chatroom pages, and those sites are becoming a bit of a hassle to keep up with considering SOX isn't very useful there. We'd also probably clear up a lot of code if we removed the if statements that check whether the topbar is the new one or old one.

What do you think?

EDIT: Just noticed SE implemented a vanilla sticky topbar: https://meta.stackexchange.com/questions/311213/can-i-please-have-the-option-to-sticky-my-top-bar-wherever-i-want?noredirect=1&lq=1