imho taskbar and systray are the basics, clock is also nice thing to have - but - not the analog one - sure it looks great, but if you need fast readout then it is not quite what you want
but the most important thing is menu that gives you most efficient way of launching your programs
sure - some people put everything into quicklaunch bars or place shortcuts on desktop, but for me it looks trashy, and if someone else need to use such machine is completly lost!
if i would want to realise theme for general public i would do it such way that menu system would be easly (drag&drop for instance) configurable and flexible
adding a couple hundreds lines to menu definition file is not the right approach, not for average mr smith