Campaigner Bob Geldof said the $50 billion (€42bn) aid package for Africa has been agreed at the G8 summit in Scotland would save 10 million lives.
Speaking at a press conference in Gleneagles, Geldof said, "today is a great day for those 10 million people".
He added: "Was this a success? On aid, ten out of 10, on debt eight out of 10."
"Time will tell, time only will tell if this has been historic or not."
Six hundred thousand people will be alive to remember this G8 in Gleneagles who would have lost their lives to a mosquito bite," Bono said, referring to the difference he thought the extra aid would make to fighting malaria.
"If an Irish rock star can quote Churchill, this is not the end of extreme poverty, but it is the beginning of the end," the U2 singer said at the end of the G8 summit in Scotland.
However, not all campaigners felt the aid package was such a success.
Dr Kumi Naidoo, chairman of the Global Call To Action Against Poverty, had earlier declared: "The people have roared but the G8 has whispered."
"The promise to deliver by 2010 is like waiting five years before responding to the Tsunami," Dr Naidoo added.
Matt Phillips, of Save The Children, said "The agreement today is only one step forward."
"The giant leap to make 2005 a breakthrough year to make child poverty history is yet to come."
Oxfam head of policy Jo Leadbeater said "the outcome here in Gleneagles has fallen short of the hopes of the millions around the world campaigning for a momentous breakthrough."