One of the best summaries of the current argument raging in the economics profession is here. This table is pretty compelling:
The impact of a difference of 1% or 2% on economic performance 10 or 20 years from now is LARGE. This is an important issue, even using the revised numbers.
The debt-to-GDP levels are given in the left-hand column. The next two columns show the annual economic growth rates estimated by Reinhart and Rogoff and then by the challenging economists from the University of Massachusetts. (They are Thomas Herndon, Michael Ash and Robert Pollin; Reinhart and Rogoff are both at Harvard.)
Debt/GDP Annual economic growth, 1945-2009
0-30% 4.1% 4.2%
30-60 2.8 3.1
60-90 2.8 3.2
90+ -0.1 2.2