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No.  With one line one person slowing down a register doesn't slow down the line.
The one line method preserves the "first come first serve" custom which is the fairest way to serve people. 
With two lines, one will be faster than the other and so some people get lucky while others get unlucky.  People usually don't like to gamble with their time in line.  If they want to gamble, they'll go to the casino. >

The one long line looks more intimidating, but it is definitely better.  That line moves fast, and even if someone has a big order or something else that slows down the transaction, the other registers keep on going pulling from the one line.
I wish more places did this.