[Hamuko]

I still hate the new tabs after having used the Developer Edition for a while. There's absolutely no separators between tabs, making it hard to see tab boundaries. Having the tabs on a separate background colour also helps to quickly see which part of the chrome is the tab bar and which is the address bar. Now they're the same colour.

FWIW, Chrome has separators between tabs as well as better contrast between the address bar section and the tab section (1.31:1 for Chrome, 1.08:1 for Firefox).