indistinguishable active tab in gnome terminal
Solution 1:
gnome-terminal-3.x uses Gtk+3, so changing the Gtk+2 theme indeed does not change the look of your gnome-terminal. There's no Gtk+3 theme switcher except for the Gnome3 tool yet afaik, so you're probably pretty much stuck with the look of it. An alternative would be downgrading to gnome-terminal-2.x.
Solution 2:
Adwaita theme is a GTK3 theme compatible with GTK2. He is in the package gnome-themes-standard:3.0.2-1
If you don't want to change your theme, you can use Adwaita only for the controls:
$ gnome-appearance-properties
Customize
Controls
And choose Adwaita. Controls will change your buttons, toolbars, windows list ... AND tabs appearance.
http://lists.debian.org/debian-gtk-gnome/2011/06/msg00015.html