Everyones internal organs burst inside their bodies causing painful death, the plane disintigrates due to the stresses on the main structure and the fuel tanks ignite - to put it bluntly.
The De-Havilland Comet is still flying with the RAF; nowadays it's called a Nimrod. Used on maritime reconnaissance and providing communications on long range cover on Search And Rescue (SAR) missions within the UK and further a field.
Yes - but the Nimrod is a much more advanced and highly modified version of the comet - the structual design flaws have been ironed out so metal fatigue is no longer a risk. There are no more commercial versions of the comet in flying condition today.