I love Xmonad, but I think gnome-panel goes with it way better than xmobar.
Although I don't use the menu's that often, and I hate digging down into menus - I find they are really useful for reminding myself quickly which programs I have installed. I only really noticed this when I tried out Unity. I had no feeling of what was installed or what was not. For example I went to install transmission - and then found it was already there after I had dug through to the software center. That feels really wrong.