Without it, Black Caps wicketkeeper Brendon McCullum would be back in the shed and his side would be 276 for seven.
Pakistan seam bowler Mohammad Asif probably does not feel the same way.
He had two referrals go against him on the opening day of the first test in Dunedin yesterday.
He asked umpire Billy Doctrove to go upstairs when he struck Ross Taylor on the pad, only to have the not out decision confirmed.
And on the penultimate ball of the day he thought he had got rid of McCullum for 25 when umpire Simon Taufel raised his finger and gave the New Zealander out lbw.
McCullum asked for the decision to be referred to third umpire Rudi Koertzen, who, with the benefit of ball-tracking technology, reversed the decision.
The DRS is being used for the first time after worldwide trials during the past year.
The system allows teams to make two unsuccessful referrals per innings.
International Cricket Council umpires manager Doug Cowie believes the system worked well.
The delivery that struck Taylor had hit in line but technology revealed the centre of the ball had not struck inside the wicket-to-wicket zone.
Under the guidelines, the batsman has to be given the benefit of the doubt.
"There is a margin for error and that goes in favour of the batsman," Cowie said.
In the McCullum incident, the replays showed the ball had struck outside the line so the decision was reversed.
"No umpire likes to make mistakes but I think umpires would rather see their mistakes corrected before they go to bed."
Last year, Daniel Flynn missed out on a maiden test hundred at the University Oval when he was given out on 95 after West Indies skipper Chris Gayle successfully referred the decision to the third official.
The system was still being trialled then, and Cowie believes under the new guidelines Flynn would not have been given out.
"It was overturned on a small amount of evidence. This year we insist there is more clear evidence shown to the third umpire before the decision is changed."
