Battery life is definitely an issue with smart phones at the moment (don't forget that the Desire has a 1Ghz processor, that's better than some netbooks so the battery life is quite impressive really!) but don't buy in to the automatic task killer apps: they'll actually use up more battery by sitting there running all the time and cause certain apps not to work properly until you bypass them (the first time it kills your alarm clock and you oversleep for example!). Android actually stops processing apps that are in the background (unless they're busy) anyway so killing them is a waste of time. The other argument is to free up RAM: Android automatically kills inactive apps to free up more RAM if it needs it.