Lehmann took over from Mickey Arthur after the South African mentor was sacked just 13 days before the previous Ashes series in England.
Australia didn't win a Test in that series, but are now on the verge of claiming the Ashes for the first time since 2007 with a third successive Test victory in the return series.
Speaking after Australia dominated the fourth day of the third Test at the WACA Ground to move to within five wickets of a series win, second-innings centurion Watson said the home team was a rejuvenated unit under Lehmann. "We are playing a lot better cricket," Watson told reporters.
"Even in our one-day cricket leading up to this Ashes series we were playing the Australian brand of cricket, taking the game on. "Everyone is performing well and putting their hand up when the team needs it."
Watson infamously clashed with Arthur when he was one of four players who failed to submit feedback requested by team management in India earlier this year, as Australia were on the wrong end of a clean sweep in a four-Test series.
He said Lehmann had been a breath of fresh air. "From the first week or so when Darren Lehmann took over, it has been the most exciting time in my career to be part of the Australian team," he said.
"To see how everyone is continuing to grow under Darren's leadership has really been a special time in everyone's career and especially mine.
"To know the ups and downs we have been through over the last three or four years. "We are playing the way we know we are going to get the best out of ourselves."
Although Lehmann's team failed to win a Test in England, they took out the subsequent one-day series and then narrowly lost a limited-overs series in India.
For so long the dominant team in world cricket, Australia are currently the fifth-ranked nation in Test cricket and second in one-day cricket.