At least in GNOME and XFCE you can decrease the default font size, which is what I did right after installing Debian with XFCE. XFCE also has really slim button

At least in GNOME and XFCE you can decrease the default font size, which is what I did right after installing Debian with XFCE. XFCE also has really slim buttons and borders. Sadly the file manager, Thunar, is not slim at all. So if you have not already given XFCE a try I recommend you do. Personally I wont use Unity until the skin i as slim as XFCE.