S&P's US Debt Downgrade Impact?

So the United States lost its AAA credit rating from S&P's. After the US debt downgrade, how is this going to impact the country?
The U.S. government debt was considered the safest financial security in the world, I wonder what is going to happen now that S&P changed that.
The impact is not going to be minimal, I think investors are going to sell like mad and the stock market is definitely going down. In your opinion, is the impact of the US debt downgrade going to affects us regular citizens in a noticeable way?

A downgrade may ward off investors from buying U.S. debt and increase the country's cost to borrow money.
This is what I think the impact of the S&P's downgrade will be.
Benchmark long-term interest rates will rise. Borrowing costs across a number of spectrums over time will rise, making loans and bonds more expensive.
I was not surprised by this move, S&P first put the US government on notice a few months ago that a debt downgrade was possible unless Congress came up with a good deficit reduction plan.
Since that never happened, S&P had to downgrade the credit rating.