I also use Ubuntu almost exclusively. My biggest complaint is with the panel. It doesn't make sense to me to have both the 'notification area' and 'indicator applet.' Why is my wifi status indicator in a separate grouping from the battery and sound indicators? I prefer to have any sort of important indicators grouped together. When I place the groups side by side, there's a visible divider between them. I feel this is a waste of space and is detrimental to the overall look and feel. Another issue with this is that when I switch screen resolution or use an external monitor, the positions of the groups shift. I'd prefer if they were always just docked against the edge of my screen.