According to the Associated Press, Obama's budget proposal would reduce the deficit by over $1 trillion -- two thirds of that will come from spending cuts. Four hundred billion of those cuts will come from Obama's recently proposed spending freeze. Since that freeze does not allow for spending to keep up with inflation, it acts in effect as a reduced spending cap.
Note, the new budget year begins in October, so this proposal won't really interact with the current spending cut fight on Capitol Hill. But Republicans are already basically rejecting it out of hand. House Budget Committee Chairman Paul Ryan said Sunday on Fox News that the plan will offer "paltry savings."
"It looks like to me that it is going to be very small on spending discipline and a lot of new spending so-called investments," he said.